Bump Citus version to 9.5.12

We should not omit to free PGResult when we receive single tuple result
from an internal backend.
Single tuple results are normally freed by our ReceiveResults for
`tupleDescriptor != NULL` flow but not for those with `tupleDescriptor
== NULL`. See PR #6722 for details.

DESCRIPTION: Fixes memory leak issue with query results that returns
single row.

(cherry picked from commit 9e69dd0e7f)

.circleci/config.yml

@@ -5,47 +5,32 @@ orbs:
 
 jobs:
 
-  build-11:
+  build:
+    description: Build the citus extension
+    parameters:
+      pg_major:
+        description: postgres major version building citus for
+        type: integer
+      image:
+        description: docker image to use for the build
+        type: string
+        default: citus/extbuilder
+      image_tag:
+        description: tag to use for the docker image
+        type: string
     docker:
-      - image: 'citus/extbuilder:11.9'
+      - image: '<< parameters.image >>:<< parameters.image_tag >>'
     steps:
       - checkout
       - run:
           name: 'Configure, Build, and Install'
-          command: build-ext
+          command: |
+            ./ci/build-citus.sh
       - persist_to_workspace:
           root: .
           paths:
-            - build-11/*
-            - install-11.tar
-
-  build-12:
-    docker:
-      - image: 'citus/extbuilder:12.4'
-    steps:
-      - checkout
-      - run:
-          name: 'Configure, Build, and Install'
-          command: build-ext
-      - persist_to_workspace:
-          root: .
-          paths:
-            - build-12/*
-            - install-12.tar
-
-  build-13:
-    docker:
-      - image: 'citus/extbuilder:13.0'
-    steps:
-      - checkout
-      - run:
-          name: 'Configure, Build, and Install'
-          command: build-ext
-      - persist_to_workspace:
-          root: .
-          paths:
-            - build-13/*
-            - install-13.tar
+            - build-<< parameters.pg_major >>/*
+            - install-<<parameters.pg_major >>.tar
 
   check-style:
     docker:
@@ -91,6 +76,7 @@ jobs:
       - run:
           name: 'Check if all CI scripts are actually run'
           command: ci/check_all_ci_scripts_are_run.sh
+
   check-sql-snapshots:
     docker:
       - image: 'citus/extbuilder:latest'
@@ -99,392 +85,230 @@ jobs:
       - run:
           name: 'Check Snapshots'
           command: ci/check_sql_snapshots.sh
-  test-11_check-multi:
+
+  test-pg-upgrade:
+    description: Runs postgres upgrade tests
+    parameters:
+      old_pg_major:
+        description: 'postgres major version to use before the upgrade'
+        type: integer
+      new_pg_major:
+        description: 'postgres major version to upgrade to'
+        type: integer
+      image:
+        description: 'docker image to use as for the tests'
+        type: string
+        default: citus/pgupgradetester
+      image_tag:
+        description: 'docker image tag to use'
+        type: string
+        default: latest
     docker:
-      - image: 'citus/exttester:11.9'
+      - image: '<< parameters.image >>:<< parameters.image_tag >>'
     working_directory: /home/circleci/project
     steps:
       - checkout
       - attach_workspace:
           at: .
       - run:
-          name: 'Install and Test (check-multi)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-multi'
-          no_output_timeout: 2m
-      - codecov/upload:
-          flags: 'test_11,multi'
-
-
-
-  test-11_check-vanilla:
-    docker:
-      - image: 'citus/exttester:11.9'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
+          name: 'Install Extension'
+          command: |
+            tar xfv "${CIRCLE_WORKING_DIRECTORY}/install-<< parameters.old_pg_major >>.tar" --directory /
+            tar xfv "${CIRCLE_WORKING_DIRECTORY}/install-<< parameters.new_pg_major >>.tar" --directory /
       - run:
-          name: 'Install and Test (check-vanilla)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-vanilla'
-          no_output_timeout: 2m
-      - codecov/upload:
-          flags: 'test_11,vanilla'
-
-  test-11_check-mx:
-    docker:
-      - image: 'citus/exttester:11.9'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
-      - run:
-          name: 'Install and Test (check-mx)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-multi-mx'
-          no_output_timeout: 2m
-      - codecov/upload:
-          flags: 'test_11,mx'
-
-  test-11_check-worker:
-    docker:
-      - image: 'citus/exttester:11.9'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
-      - run:
-          name: 'Install and Test (check-worker)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-worker'
-          no_output_timeout: 2m
-      - codecov/upload:
-          flags: 'test_11,worker'
-
-  test-11_check-isolation:
-    docker:
-      - image: 'citus/exttester:11.9'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
-      - run:
-          name: 'Install and Test (check-isolation)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-isolation'
-          no_output_timeout: 2m
-      - codecov/upload:
-          flags: 'test_11,isolation'
-  test-11_check-follower-cluster:
-    docker:
-      - image: 'citus/exttester:11.9'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
+          name: 'Configure'
+          command: |
+            chown -R circleci .
+            gosu circleci ./configure
       - run:
           name: 'Enable core dumps'
-          command: 'ulimit -c unlimited'
+          command: |
+            ulimit -c unlimited
       - run:
-          name: 'Install and Test (follower-cluster)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-follower-cluster'
+          name: 'Install and test postgres upgrade'
+          command: |
+            gosu circleci \
+              make -C src/test/regress \
+                check-pg-upgrade \
+                old-bindir=/usr/lib/postgresql/<< parameters.old_pg_major >>/bin \
+                new-bindir=/usr/lib/postgresql/<< parameters.new_pg_major >>/bin
           no_output_timeout: 2m
       - run:
+          name: 'Regressions'
+          command: |
+            if [ -f "src/test/regress/regression.diffs" ]; then
+              cat src/test/regress/regression.diffs
+              exit 1
+            fi
+          when: on_fail
+      - run:
+          name: 'Copy coredumps'
           command: |
             mkdir -p /tmp/core_dumps
-            cp core.* /tmp/core_dumps
+            if ls core.* 1> /dev/null 2>&1; then
+                cp core.* /tmp/core_dumps
+            fi
+          when: on_fail
+      - store_artifacts:
+          name: 'Save regressions'
+          path: src/test/regress/regression.diffs
+          when: on_fail
+      - store_artifacts:
+          name: 'Save core dumps'
+          path: /tmp/core_dumps
           when: on_fail
       - codecov/upload:
-          flags: 'test_11,follower-cluster'
-      - store_artifacts:
-          path: '/tmp/core_dumps'
-  test-11_check-failure:
+          flags: 'test_<< parameters.old_pg_major >>_<< parameters.new_pg_major >>,upgrade'
+
+  test-citus-upgrade:
+    description: Runs citus upgrade tests
+    parameters:
+      pg_major:
+        description: "postgres major version"
+        type: integer
+      image:
+        description: 'docker image to use as for the tests'
+        type: string
+        default: citus/citusupgradetester
+      image_tag:
+        description: 'docker image tag to use'
+        type: string
     docker:
-      - image: 'citus/failtester:11.9'
+      - image: '<< parameters.image >>:<< parameters.image_tag >>'
     working_directory: /home/circleci/project
     steps:
       - checkout
       - attach_workspace:
           at: .
       - run:
-          name: 'Install and Test (check-failure)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-failure'
-          no_output_timeout: 2m
-
-  test-11-12_check-pg-upgrade:
-    docker:
-      - image: 'citus/pgupgradetester:latest'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
-      - run:
-          name: 'Install and test postgres upgrade'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext --target check-pg-upgrade --old-pg-version 11 --new-pg-version 12'
-          no_output_timeout: 2m
-
-  test-12-13_check-pg-upgrade:
-    docker:
-      - image: 'citus/pgupgradetester:latest'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
-      - run:
-          name: 'Install and test postgres upgrade'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext --target check-pg-upgrade --old-pg-version 12 --new-pg-version 13'
-          no_output_timeout: 2m
-
-  test-12_check-multi:
-    docker:
-      - image: 'citus/exttester:12.4'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
-      - run:
-          name: 'Install and Test (check-multi)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-multi'
-          no_output_timeout: 2m
-      - codecov/upload:
-          flags: 'test_12,multi'
-  test-12_check-vanilla:
-    docker:
-      - image: 'citus/exttester:12.4'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
-      - run:
-          name: 'Install and Test (check-vanilla)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-vanilla'
-          no_output_timeout: 2m
-      - codecov/upload:
-          flags: 'test_12,vanilla'
-
-  test-12_check-mx:
-    docker:
-      - image: 'citus/exttester:12.4'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
-      - run:
-          name: 'Install and Test (check-mx)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-multi-mx'
-          no_output_timeout: 2m
-      - codecov/upload:
-          flags: 'test_12,mx'
-
-  test-12_check-isolation:
-    docker:
-      - image: 'citus/exttester:12.4'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-           at: .
-      - run:
-          name: 'Install and Test (check-isolation)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-isolation'
-          no_output_timeout: 2m
-      - codecov/upload:
-          flags: 'test_12,isolation'
-
-  test-12_check-worker:
-    docker:
-      - image: 'citus/exttester:12.4'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-           at: .
-      - run:
-          name: 'Install and Test (check-worker)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-worker'
-          no_output_timeout: 2m
-      - codecov/upload:
-          flags: 'test_12,worker'
-
-  test-12_check-follower-cluster:
-    docker:
-      - image: 'citus/exttester:12.4'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
+          name: 'Configure'
+          command: |
+            chown -R circleci .
+            gosu circleci ./configure
       - run:
           name: 'Enable core dumps'
-          command: 'ulimit -c unlimited'
-      - run:
-          name: 'Install and Test (follower-cluster)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-follower-cluster'
-          no_output_timeout: 2m
-      - run:
           command: |
-            mkdir -p /tmp/core_dumps
-            cp core.* /tmp/core_dumps
-          when: on_fail
-      - codecov/upload:
-          flags: 'test_12,follower-cluster'
-      - store_artifacts:
-          path: '/tmp/core_dumps'
-
-  test-12_check-failure:
-    docker:
-      - image: 'citus/failtester:12.4'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
-      - run:
-          name: 'Install and Test (check-failure)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-failure'
-          no_output_timeout: 2m
-
-  test-11_check-citus-upgrade:
-    docker:
-      - image: 'citus/citusupgradetester:11.9'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
+            ulimit -c unlimited
       - run:
           name: 'Install and test citus upgrade'
           command: |
-           chown -R circleci:circleci /home/circleci
-           install-and-test-ext --target check-citus-upgrade --citus-pre-tar /install-pg11-citusv8.0.0.tar
-           install-and-test-ext --target check-citus-upgrade --citus-pre-tar /install-pg11-citusv8.1.0.tar
-           install-and-test-ext --target check-citus-upgrade --citus-pre-tar /install-pg11-citusv8.2.0.tar
-           install-and-test-ext --target check-citus-upgrade --citus-pre-tar /install-pg11-citusv8.3.0.tar
+            # run make check-citus-upgrade for all citus versions
+            # the image has ${CITUS_VERSIONS} set with all verions it contains the binaries of
+            for citus_version in ${CITUS_VERSIONS}; do \
+              gosu circleci \
+                make -C src/test/regress \
+                  check-citus-upgrade \
+                  bindir=/usr/lib/postgresql/${PG_MAJOR}/bin \
+                  citus-pre-tar=/install-pg11-citus${citus_version}.tar \
+                  citus-post-tar=/home/circleci/project/install-$PG_MAJOR.tar; \
+            done;
 
-           install-and-test-ext --target check-citus-upgrade-mixed --citus-pre-tar /install-pg11-citusv8.0.0.tar
-           install-and-test-ext --target check-citus-upgrade-mixed --citus-pre-tar /install-pg11-citusv8.1.0.tar
-           install-and-test-ext --target check-citus-upgrade-mixed --citus-pre-tar /install-pg11-citusv8.2.0.tar
-           install-and-test-ext --target check-citus-upgrade-mixed --citus-pre-tar /install-pg11-citusv8.3.0.tar
-          no_output_timeout: 2m
-
-  test-13_check-multi:
-    docker:
-      - image: 'citus/exttester:13.0'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
-      - run:
-          name: 'Install and Test (check-multi)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-multi'
-          no_output_timeout: 2m
-      - codecov/upload:
-          flags: 'test_13,multi'
-
-  test-13_check-mx:
-    docker:
-      - image: 'citus/exttester:13.0'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
-      - run:
-          name: 'Install and Test (check-mx)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-multi-mx'
-          no_output_timeout: 2m
-      - codecov/upload:
-          flags: 'test_13,mx'
-
-  test-13_check-vanilla:
-    docker:
-      - image: 'citus/exttester:13.0'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
-      - run:
-          name: 'Install and Test (check-vanilla)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-vanilla'
-          no_output_timeout: 2m
-      - codecov/upload:
-          flags: 'test_13,vanilla'
-
-  test-13_check-worker:
-    docker:
-      - image: 'citus/exttester:13.0'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-           at: .
-      - run:
-          name: 'Install and Test (check-worker)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-worker'
-          no_output_timeout: 2m
-      - codecov/upload:
-          flags: 'test_13,worker'
-
-  test-13_check-isolation:
-    docker:
-      - image: 'citus/exttester:13.0'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-           at: .
-      - run:
-          name: 'Install and Test (check-isolation)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-isolation'
-          no_output_timeout: 2m
-      - codecov/upload:
-          flags: 'test_13,isolation'
-
-  test-13_check-follower-cluster:
-    docker:
-      - image: 'citus/exttester:13.0'
-    working_directory: /home/circleci/project
-    steps:
-      - checkout
-      - attach_workspace:
-          at: .
-      - run:
-          name: 'Enable core dumps'
-          command: 'ulimit -c unlimited'
-      - run:
-          name: 'Install and Test (follower-cluster)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-follower-cluster'
+            # run make check-citus-upgrade-mixed for all citus versions
+            # the image has ${CITUS_VERSIONS} set with all verions it contains the binaries of
+            for citus_version in ${CITUS_VERSIONS}; do \
+              gosu circleci \
+                make -C src/test/regress \
+                  check-citus-upgrade-mixed \
+                  bindir=/usr/lib/postgresql/${PG_MAJOR}/bin \
+                  citus-pre-tar=/install-pg11-citus${citus_version}.tar \
+                  citus-post-tar=/home/circleci/project/install-$PG_MAJOR.tar; \
+            done;
           no_output_timeout: 2m
       - run:
+          name: 'Regressions'
+          command: |
+            if [ -f "src/test/regress/regression.diffs" ]; then
+              cat src/test/regress/regression.diffs
+              exit 1
+            fi
+          when: on_fail
+      - run:
+          name: 'Copy coredumps'
           command: |
             mkdir -p /tmp/core_dumps
-            cp core.* /tmp/core_dumps
+            if ls core.* 1> /dev/null 2>&1; then
+                cp core.* /tmp/core_dumps
+            fi
+          when: on_fail
+      - store_artifacts:
+          name: 'Save regressions'
+          path: src/test/regress/regression.diffs
+          when: on_fail
+      - store_artifacts:
+          name: 'Save core dumps'
+          path: /tmp/core_dumps
           when: on_fail
       - codecov/upload:
-          flags: 'test_13,follower-cluster'
-      - store_artifacts:
-          path: '/tmp/core_dumps'
+          flags: 'test_<< parameters.pg_major >>,upgrade'
 
-  test-13_check-failure:
+  test-citus:
+    description: Runs the common tests of citus
+    parameters:
+      pg_major:
+        description: "postgres major version"
+        type: integer
+      image:
+        description: 'docker image to use as for the tests'
+        type: string
+        default: citus/exttester
+      image_tag:
+        description: 'docker image tag to use'
+        type: string
+      make:
+        description: "make target"
+        type: string
     docker:
-      - image: 'citus/failtester:13.0'
+      - image: '<< parameters.image >>:<< parameters.image_tag >>'
     working_directory: /home/circleci/project
     steps:
       - checkout
       - attach_workspace:
           at: .
       - run:
-          name: 'Install and Test (check-failure)'
-          command: 'chown -R circleci:circleci /home/circleci && install-and-test-ext check-failure'
+          name: 'Install Extension'
+          command: |
+            tar xfv "${CIRCLE_WORKING_DIRECTORY}/install-${PG_MAJOR}.tar" --directory /
+      - run:
+          name: 'Configure'
+          command: |
+            chown -R circleci .
+            gosu circleci ./configure
+      - run:
+          name: 'Enable core dumps'
+          command: |
+            ulimit -c unlimited
+      - run:
+          name: 'Run Test'
+          command: |
+            gosu circleci make -C src/test/regress << parameters.make >>
           no_output_timeout: 2m
+      - run:
+          name: 'Regressions'
+          command: |
+            if [ -f "src/test/regress/regression.diffs" ]; then
+              cat src/test/regress/regression.diffs
+              exit 1
+            fi
+          when: on_fail
+      - run:
+          name: 'Copy coredumps'
+          command: |
+            mkdir -p /tmp/core_dumps
+            if ls core.* 1> /dev/null 2>&1; then
+                cp core.* /tmp/core_dumps
+            fi
+          when: on_fail
+      - store_artifacts:
+          name: 'Save regressions'
+          path: src/test/regress/regression.diffs
+          when: on_fail
+      - store_artifacts:
+          name: 'Save core dumps'
+          path: /tmp/core_dumps
+          when: on_fail
+      - codecov/upload:
+          flags: 'test_<< parameters.pg_major >>,<< parameters.make >>'
+          when: always
 
   check-merge-to-enterprise:
     docker:
@@ -495,6 +319,7 @@ jobs:
       - run:
           command: |
             ci/check_enterprise_merge.sh
+
   ch_benchmark:
     docker:
       - image: buildpack-deps:stretch
@@ -509,6 +334,7 @@ jobs:
             sh run_hammerdb.sh citusbot_ch_benchmark_rg
           name: install dependencies and run ch_benchmark tests
           no_output_timeout: 20m
+
   tpcc_benchmark:
     docker:
       - image: buildpack-deps:stretch
@@ -524,7 +350,6 @@ jobs:
           name: install dependencies and run ch_benchmark tests
           no_output_timeout: 20m
 
-
 workflows:
   version: 2
   build_and_test:
@@ -536,70 +361,173 @@ workflows:
               ignore:
                 - /release-[0-9]+\.[0-9]+.*/ # match with releaseX.Y.*
 
-
-      - build-11
-      - build-12
-      - build-13
+      - build:
+          name: build-11
+          pg_major: 11
+          image_tag: '11.9'
+      - build:
+          name: build-12
+          pg_major: 12
+          image_tag: '12.4'
+      - build:
+          name: build-13
+          pg_major: 13
+          image_tag: '13.0'
 
       - check-style
       - check-sql-snapshots
 
-      - test-11_check-multi:
+      - test-citus:
+          name: 'test-11_check-multi'
+          pg_major: 11
+          image_tag: '11.9'
+          make: check-multi
           requires: [build-11]
-      - test-11_check-vanilla:
+      - test-citus:
+          name: 'test-11_check-mx'
+          pg_major: 11
+          image_tag: '11.9'
+          make: check-multi-mx
           requires: [build-11]
-      - test-11_check-isolation:
+      - test-citus:
+          name: 'test-11_check-vanilla'
+          pg_major: 11
+          image_tag: '11.9'
+          make: check-vanilla
           requires: [build-11]
-      - test-11_check-mx:
+      - test-citus:
+          name: 'test-11_check-isolation'
+          pg_major: 11
+          image_tag: '11.9'
+          make: check-isolation
           requires: [build-11]
-      - test-11_check-worker:
+      - test-citus:
+          name: 'test-11_check-worker'
+          pg_major: 11
+          image_tag: '11.9'
+          make: check-worker
           requires: [build-11]
-      - test-11_check-follower-cluster:
+      - test-citus:
+          name: 'test-11_check-follower-cluster'
+          pg_major: 11
+          image_tag: '11.9'
+          make: check-follower-cluster
           requires: [build-11]
-      - test-11_check-failure:
+      - test-citus:
+          name: 'test-11_check-failure'
+          pg_major: 11
+          image: citus/failtester
+          image_tag: '11.9'
+          make: check-failure
           requires: [build-11]
 
-      - test-12_check-multi:
+      - test-citus:
+          name: 'test-12_check-multi'
+          pg_major: 12
+          image_tag: '12.4'
+          make: check-multi
           requires: [build-12]
-      - test-12_check-vanilla:
+      - test-citus:
+          name: 'test-12_check-mx'
+          pg_major: 12
+          image_tag: '12.4'
+          make: check-multi-mx
           requires: [build-12]
-      - test-12_check-isolation:
+      - test-citus:
+          name: 'test-12_check-vanilla'
+          pg_major: 12
+          image_tag: '12.4'
+          make: check-vanilla
           requires: [build-12]
-      - test-12_check-mx:
+      - test-citus:
+          name: 'test-12_check-isolation'
+          pg_major: 12
+          image_tag: '12.4'
+          make: check-isolation
           requires: [build-12]
-      - test-12_check-worker:
+      - test-citus:
+          name: 'test-12_check-worker'
+          pg_major: 12
+          image_tag: '12.4'
+          make: check-worker
           requires: [build-12]
-      - test-12_check-follower-cluster:
+      - test-citus:
+          name: 'test-12_check-follower-cluster'
+          pg_major: 12
+          image_tag: '12.4'
+          make: check-follower-cluster
           requires: [build-12]
-      - test-12_check-failure:
+      - test-citus:
+          name: 'test-12_check-failure'
+          pg_major: 12
+          image: citus/failtester
+          image_tag: '12.4'
+          make: check-failure
           requires: [build-12]
 
-      - test-13_check-multi:
+      - test-citus:
+          name: 'test-13_check-multi'
+          pg_major: 13
+          image_tag: '13.0'
+          make: check-multi
           requires: [build-13]
-      - test-13_check-vanilla:
+      - test-citus:
+          name: 'test-13_check-mx'
+          pg_major: 13
+          image_tag: '13.0'
+          make: check-multi-mx
           requires: [build-13]
-      - test-13_check-isolation:
+      - test-citus:
+          name: 'test-13_check-vanilla'
+          pg_major: 13
+          image_tag: '13.0'
+          make: check-vanilla
           requires: [build-13]
-      - test-13_check-mx:
+      - test-citus:
+          name: 'test-13_check-isolation'
+          pg_major: 13
+          image_tag: '13.0'
+          make: check-isolation
           requires: [build-13]
-      - test-13_check-worker:
+      - test-citus:
+          name: 'test-13_check-worker'
+          pg_major: 13
+          image_tag: '13.0'
+          make: check-worker
           requires: [build-13]
-      - test-13_check-follower-cluster:
-          requires: [build-13]
-      - test-13_check-failure:
+      - test-citus:
+          name: 'test-13_check-follower-cluster'
+          pg_major: 13
+          image_tag: '13.0'
+          make: check-follower-cluster
           requires: [build-13]
 
-      - test-11-12_check-pg-upgrade:
-          requires:
-            - build-11
-            - build-12
+      - test-citus:
+          name: 'test-13_check-failure'
+          pg_major: 13
+          image: citus/failtester
+          image_tag: '13.0'
+          make: check-failure
+          requires: [build-13]
 
-      - test-12-13_check-pg-upgrade:
-          requires:
-            - build-12
-            - build-13
+      - test-pg-upgrade:
+          name: 'test-11-12_check-pg-upgrade'
+          old_pg_major: 11
+          new_pg_major: 12
+          image_tag: latest
+          requires: [build-11,build-12]
 
-      - test-11_check-citus-upgrade:
+      - test-pg-upgrade:
+          name: 'test-12-13_check-pg-upgrade'
+          old_pg_major: 12
+          new_pg_major: 13
+          image_tag: latest
+          requires: [build-12,build-13]
+
+      - test-citus-upgrade:
+          name: test-11_check-citus-upgrade
+          pg_major: 11
+          image_tag: '11.9'
           requires: [build-11]
 
       - ch_benchmark:

CHANGELOG.md

@@ -1,3 +1,187 @@
+### citus v9.5.12 (April 20, 2023) ###
+
+* Fixes a crash that occurs when the aggregate that cannot be pushed-down
+  returns empty result from a worker (#5679)
+
+* Fixes memory leak issue with query results that returns single row (#6724)
+
+* Prevents alter table functions from dropping extensions (#5974)
+
+### citus v9.5.10 (November 8, 2021) ###
+
+* Fixes a release problem in 9.5.9
+
+### citus v9.5.9 (November 8, 2021) ###
+
+* Fixes a bug preventing `INSERT SELECT .. ON CONFLICT` with a constraint name
+  on local shards
+
+* Fixes a bug with local cached plans on tables with dropped columns
+
+* Fixes a crash in queries with a modifying `CTE` and a `SELECT`
+  without `FROM`
+
+* Fixes a missing `FROM` clause entry error
+
+* Fixes a missing intermediate result when coordinator is in metadata
+
+* Reinstates optimisation for uniform shard interval ranges
+
+### citus v9.5.8 (September 15, 2021) ###
+
+* Fixes a bug that caused `worker_append_table_to_shard` to write as superuser
+
+* Fixes a use after free issue that could happen when altering a distributed
+  table
+
+### citus v9.5.7 (August 16, 2021) ###
+
+* Allows more graceful failovers when replication factor > 1
+
+* Fixes a bug that causes partitions to have wrong distribution key after
+  `DROP COLUMN`
+
+* Improves master_update_table_statistics and provides distributed deadlock
+  detection
+
+### citus v9.5.6 (July 8, 2021) ###
+
+* Fixes minor bug in `citus_prepare_pg_upgrade` that caused it to lose its
+  idempotency
+
+### citus v9.5.5 (July 7, 2021) ###
+
+* Adds a configure flag to enforce security
+
+* Fixes a bug that causes pruning incorrect shard of a range distributed table
+
+* Fixes an issue that could cause citus_finish_pg_upgrade to fail
+
+### citus v9.5.4 (February 19, 2021) ###
+
+* Fixes a compatibility issue with pg_audit in utility calls
+
+### citus v9.5.3 (February 16, 2021) ###
+
+* Avoids re-using connections for intermediate results
+
+* Fixes a bug that might cause self-deadlocks when `COPY` used in xact block
+
+* Fixes a crash that occurs when distributing table after dropping foreign key
+
+### citus v9.5.2 (January 26, 2021) ###
+
+* Fixes distributed deadlock detection being blocked by metadata sync
+
+* Prevents segfaults when SAVEPOINT handling cannot recover from connection
+  failures
+
+* Fixes possible issues that might occur with single shard distributed tables
+
+### citus v9.5.1 (December 1, 2020) ###
+
+* Enables PostgreSQL's parallel queries on EXPLAIN ANALYZE
+
+* Fixes a bug that could cause excessive memory consumption when a partition is
+  created
+
+* Fixes a bug that triggers subplan executions unnecessarily with cursors
+
+* Fixes a segfault in connection management due to invalid connection hash
+  entries
+
+### citus v9.5.0 (November 10, 2020) ###
+
+* Adds support for PostgreSQL 13
+
+* Removes the task-tracker executor
+
+* Introduces citus local tables
+
+* Introduces `undistribute_table` UDF to convert tables back to postgres tables
+
+* Adds support for `EXPLAIN (ANALYZE) EXECUTE` and `EXPLAIN EXECUTE`
+
+* Adds support for `EXPLAIN (ANALYZE, WAL)` for PG13
+
+* Sorts the output of `EXPLAIN (ANALYZE)` by execution duration.
+
+* Adds support for CREATE TABLE ... USING table_access_method
+
+* Adds support for `WITH TIES` option in SELECT and INSERT SELECT queries
+
+* Avoids taking multi-shard locks on workers
+
+* Enforces `citus.max_shared_pool_size` config in COPY queries
+
+* Enables custom aggregates with multiple parameters to be executed on workers
+
+* Enforces `citus.max_intermediate_result_size` in local execution
+
+* Improves cost estimation of INSERT SELECT plans
+
+* Introduces delegation of procedures that read from reference tables
+
+* Prevents pull-push execution for simple pushdownable subqueries
+
+* Improves error message when creating a foreign key to a local table
+
+* Makes `citus_prepare_pg_upgrade` idempotent by dropping transition tables
+
+* Disallows `ON TRUE` outer joins with reference & distributed tables when
+  reference table is outer relation to avoid incorrect results
+
+* Disallows field indirection in INSERT/UPDATE queries to avoid incorrect
+  results
+
+* Disallows volatile functions in UPDATE subqueries to avoid incorrect results
+
+* Fixes CREATE INDEX CONCURRENTLY crash with local execution
+
+* Fixes `citus_finish_pg_upgrade` to drop all backup tables
+
+* Fixes a bug that cause failures when `RECURSIVE VIEW` joined reference table
+
+* Fixes DROP SEQUENCE failures when metadata syncing is enabled
+
+* Fixes a bug that caused CREATE TABLE with CHECK constraint to fail
+
+* Fixes a bug that could cause VACUUM to deadlock
+
+* Fixes master_update_node failure when no background worker slots are available
+
+* Fixes a bug that caused replica identity to not be propagated on shard repair
+
+* Fixes a bug that could cause crashes after connection timeouts
+
+* Fixes a bug that could cause crashes with certain compile flags
+
+* Fixes a bug that could cause deadlocks on CREATE INDEX
+
+* Fixes a bug with genetic query optimization in outer joins
+
+* Fixes a crash when aggregating empty tables
+
+* Fixes a crash with inserting domain constrained composite types
+
+* Fixes a crash with multi-row & router INSERT's in local execution
+
+* Fixes a possibility of doing temporary file cleanup more than once
+
+* Fixes incorrect setting of join related fields
+
+* Fixes memory issues around deparsing index commands
+
+* Fixes reference table access tracking for sequential execution
+
+* Fixes removal of a single node with only reference tables
+
+* Fixes sending commands to coordinator when it is added as a worker
+
+* Fixes write queries with const expressions and COLLATE in various places
+
+* Fixes wrong cancellation message about distributed deadlock
+
 ### citus v9.4.2 (October 21, 2020) ###
 
 * Fixes a bug that could lead to multiple maintenance daemons

Makefile.global.in

@@ -86,6 +86,7 @@ endif
 
 # Add options passed to configure or computed therein, to CFLAGS/CPPFLAGS/...
 override CFLAGS += @CFLAGS@ @CITUS_CFLAGS@
+override BITCODE_CFLAGS := $(BITCODE_CFLAGS) @CITUS_BITCODE_CFLAGS@
 ifneq ($(GIT_VERSION),)
     override CFLAGS += -DGIT_VERSION=\"$(GIT_VERSION)\"
 endif

NOTICE

@@ -0,0 +1,99 @@
+NOTICES AND INFORMATION
+Do Not Translate or Localize
+
+This software incorporates material from third parties.
+Microsoft makes certain open source code available at https://3rdpartysource.microsoft.com,
+or you may send a check or money order for US $5.00, including the product name,
+the open source component name, platform, and version number, to:
+
+Source Code Compliance Team
+Microsoft Corporation
+One Microsoft Way
+Redmond, WA 98052
+USA
+
+Notwithstanding any other terms, you may reverse engineer this software to the extent
+required to debug changes to any libraries licensed under the GNU Lesser General Public License.
+
+---------------------------------------------------------
+
+---------------------------------------------------------
+
+intel/safestringlib 245c4b8cff1d2e7338b7f3a82828fc8e72b29549 - MIT
+
+Copyright (c) 2014-2018 Intel Corporation
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
+================================================================================
+
+Copyright (C) 2012, 2013 Cisco Systems
+All rights reserved.
+
+Permission is hereby granted, free of charge, to any person
+obtaining a copy of this software and associated documentation
+files (the "Software"), to deal in the Software without
+restriction, including without limitation the rights to use,
+copy, modify, merge, publish, distribute, sublicense, and/or
+sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
+---------------------------------------------------------
+
+
+postgres/postgres 29be9983a64c011eac0b9ee29895cce71e15ea77
+
+
+PostgreSQL Database Management System
+(formerly known as Postgres, then as Postgres95)
+
+Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
+
+Portions Copyright (c) 1994, The Regents of the University of California
+
+Permission to use, copy, modify, and distribute this software and its
+documentation for any purpose, without fee, and without a written agreement
+is hereby granted, provided that the above copyright notice and this
+paragraph and the following two paragraphs appear in all copies.
+
+IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR
+DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
+LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
+DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
+
+THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
+INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATIONS TO
+PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+
+---------------------------------------------------------

cgmanifest.json

@@ -0,0 +1,47 @@
+{
+    "Registrations": [
+        {
+            "Component": {
+                "Type": "git",
+                "git": {
+                    "RepositoryUrl": "https://github.com/intel/safestringlib",
+                    "CommitHash": "245c4b8cff1d2e7338b7f3a82828fc8e72b29549"
+                }
+            },
+            "DevelopmentDependency": false
+        },
+        {
+            "Component": {
+                "Type": "git",
+                "git": {
+                    "RepositoryUrl": "https://github.com/postgres/postgres",
+                    "CommitHash": "29be9983a64c011eac0b9ee29895cce71e15ea77"
+                }
+            },
+            "license": "PostgreSQL",
+            "licenseDetail": [
+				"Portions Copyright (c) 1996-2010, The PostgreSQL Global Development Group",
+				"",
+				"Portions Copyright (c) 1994, The Regents of the University of California",
+                "",
+                "Permission to use, copy, modify, and distribute this software and its documentation for ",
+                "any purpose, without fee, and without a written agreement is hereby granted, provided ",
+                "that the above copyright notice and this paragraph and the following two paragraphs appear ",
+                "in all copies.",
+                "",
+                "IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, ",
+                "INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS ",
+                "SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE ",
+                "POSSIBILITY OF SUCH DAMAGE.",
+                "",
+                "THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT LIMITED TO, ",
+                "THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED ",
+                "HEREUNDER IS ON AN \"AS IS\" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATIONS TO PROVIDE ",
+                "MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS."
+            ],
+            "version": "0.0.1",
+            "DevelopmentDependency": false
+        }
+
+    ]
+}

ci/README.md

@@ -46,6 +46,16 @@ following:
    requires also adding a comment before explaining why this specific use of the
    function is safe.
 
+## `build-citus.sh`
+
+This is the script used during the build phase of the extension. Historically this script
+was embedded in the docker images. This made maintenance a hassle. Now it lives in tree
+with the rest of the source code.
+
+When this script fails you most likely have a build error on the postgres version it was
+building at the time of the failure. Fix the compile error and push a new version of your
+code to fix.
+
 ## `check_enterprise_merge.sh`
 
 This check exists to make sure that we can always merge the `master` branch of

ci/build-citus.sh

@@ -0,0 +1,47 @@
+#!/bin/bash
+
+# make bash behave
+set -euo pipefail
+IFS=$'\n\t'
+
+# shellcheck disable=SC1091
+source ci/ci_helpers.sh
+
+# read pg major version, error if not provided
+PG_MAJOR=${PG_MAJOR:?please provide the postgres major version}
+
+# get codename from release file
+. /etc/os-release
+codename=${VERSION#*(}
+codename=${codename%)*}
+
+# get project from argument
+project="${CIRCLE_PROJECT_REPONAME}"
+
+# we'll do everything with absolute paths
+basedir="$(pwd)"
+
+# get the project and clear out the git repo (reduce workspace size
+rm -rf "${basedir}/.git"
+
+build_ext() {
+  pg_major="$1"
+
+  builddir="${basedir}/build-${pg_major}"
+  echo "Beginning build of ${project} for PostgreSQL ${pg_major}..." >&2
+
+  # do everything in a subdirectory to avoid clutter in current directory
+  mkdir -p "${builddir}" && cd "${builddir}"
+
+  CFLAGS=-Werror "${basedir}/configure" PG_CONFIG="/usr/lib/postgresql/${pg_major}/bin/pg_config" --enable-coverage
+
+  installdir="${builddir}/install"
+  make -j$(nproc) && mkdir -p "${installdir}" && { make DESTDIR="${installdir}" install-all || make DESTDIR="${installdir}" install ; }
+
+  cd "${installdir}" && find . -type f -print > "${builddir}/files.lst"
+  tar cvf "${basedir}/install-${pg_major}.tar" `cat ${builddir}/files.lst`
+
+  cd "${builddir}" && rm -rf install files.lst && make clean
+}
+
+build_ext "${PG_MAJOR}"

configure

@@ -1,6 +1,6 @@
 #! /bin/sh
 # Guess values for system-dependent variables and create Makefiles.
-# Generated by GNU Autoconf 2.69 for Citus 9.5devel.
+# Generated by GNU Autoconf 2.69 for Citus 9.5.12.
 #
 #
 # Copyright (C) 1992-1996, 1998-2012 Free Software Foundation, Inc.
@@ -579,8 +579,8 @@ MAKEFLAGS=
 # Identity of this package.
 PACKAGE_NAME='Citus'
 PACKAGE_TARNAME='citus'
-PACKAGE_VERSION='9.5devel'
-PACKAGE_STRING='Citus 9.5devel'
+PACKAGE_VERSION='9.5.12'
+PACKAGE_STRING='Citus 9.5.12'
 PACKAGE_BUGREPORT=''
 PACKAGE_URL=''
 
@@ -627,8 +627,10 @@ POSTGRES_BUILDDIR
 POSTGRES_SRCDIR
 CITUS_LDFLAGS
 CITUS_CPPFLAGS
+CITUS_BITCODE_CFLAGS
 CITUS_CFLAGS
 GIT_BIN
+with_security_flags
 EGREP
 GREP
 CPP
@@ -664,6 +666,7 @@ infodir
 docdir
 oldincludedir
 includedir
+runstatedir
 localstatedir
 sharedstatedir
 sysconfdir
@@ -690,6 +693,7 @@ with_extra_version
 enable_coverage
 with_libcurl
 with_reports_hostname
+with_security_flags
 '
       ac_precious_vars='build_alias
 host_alias
@@ -740,6 +744,7 @@ datadir='${datarootdir}'
 sysconfdir='${prefix}/etc'
 sharedstatedir='${prefix}/com'
 localstatedir='${prefix}/var'
+runstatedir='${localstatedir}/run'
 includedir='${prefix}/include'
 oldincludedir='/usr/include'
 docdir='${datarootdir}/doc/${PACKAGE_TARNAME}'
@@ -992,6 +997,15 @@ do
   | -silent | --silent | --silen | --sile | --sil)
     silent=yes ;;
 
+  -runstatedir | --runstatedir | --runstatedi | --runstated \
+  | --runstate | --runstat | --runsta | --runst | --runs \
+  | --run | --ru | --r)
+    ac_prev=runstatedir ;;
+  -runstatedir=* | --runstatedir=* | --runstatedi=* | --runstated=* \
+  | --runstate=* | --runstat=* | --runsta=* | --runst=* | --runs=* \
+  | --run=* | --ru=* | --r=*)
+    runstatedir=$ac_optarg ;;
+
   -sbindir | --sbindir | --sbindi | --sbind | --sbin | --sbi | --sb)
     ac_prev=sbindir ;;
   -sbindir=* | --sbindir=* | --sbindi=* | --sbind=* | --sbin=* \
@@ -1129,7 +1143,7 @@ fi
 for ac_var in	exec_prefix prefix bindir sbindir libexecdir datarootdir \
 		datadir sysconfdir sharedstatedir localstatedir includedir \
 		oldincludedir docdir infodir htmldir dvidir pdfdir psdir \
-		libdir localedir mandir
+		libdir localedir mandir runstatedir
 do
   eval ac_val=\$$ac_var
   # Remove trailing slashes.
@@ -1242,7 +1256,7 @@ if test "$ac_init_help" = "long"; then
   # Omit some internal or obsolete options to make the list less imposing.
   # This message is too long to be a string in the A/UX 3.1 sh.
   cat <<_ACEOF
-\`configure' configures Citus 9.5devel to adapt to many kinds of systems.
+\`configure' configures Citus 9.5.12 to adapt to many kinds of systems.
 
 Usage: $0 [OPTION]... [VAR=VALUE]...
 
@@ -1282,6 +1296,7 @@ Fine tuning of the installation directories:
   --sysconfdir=DIR        read-only single-machine data [PREFIX/etc]
   --sharedstatedir=DIR    modifiable architecture-independent data [PREFIX/com]
   --localstatedir=DIR     modifiable single-machine data [PREFIX/var]
+  --runstatedir=DIR       modifiable per-process data [LOCALSTATEDIR/run]
   --libdir=DIR            object code libraries [EPREFIX/lib]
   --includedir=DIR        C header files [PREFIX/include]
   --oldincludedir=DIR     C header files for non-gcc [/usr/include]
@@ -1303,7 +1318,7 @@ fi
 
 if test -n "$ac_init_help"; then
   case $ac_init_help in
-     short | recursive ) echo "Configuration of Citus 9.5devel:";;
+     short | recursive ) echo "Configuration of Citus 9.5.12:";;
    esac
   cat <<\_ACEOF
 
@@ -1323,6 +1338,7 @@ Optional Packages:
   --with-reports-hostname=HOSTNAME
                           Use HOSTNAME as hostname for statistics collection
                           and update checks
+  --with-security-flags   use security flags
 
 Some influential environment variables:
   PG_CONFIG   Location to find pg_config for target PostgreSQL instalation
@@ -1403,7 +1419,7 @@ fi
 test -n "$ac_init_help" && exit $ac_status
 if $ac_init_version; then
   cat <<\_ACEOF
-Citus configure 9.5devel
+Citus configure 9.5.12
 generated by GNU Autoconf 2.69
 
 Copyright (C) 2012 Free Software Foundation, Inc.
@@ -1886,7 +1902,7 @@ cat >config.log <<_ACEOF
 This file contains any messages produced by compilers while
 running configure, to aid debugging if configure makes a mistake.
 
-It was created by Citus $as_me 9.5devel, which was
+It was created by Citus $as_me 9.5.12, which was
 generated by GNU Autoconf 2.69.  Invocation command line was
 
   $ $0 $@
@@ -4327,6 +4343,48 @@ if test x"$citusac_cv_prog_cc_cflags__Werror_return_type" = x"yes"; then
   CITUS_CFLAGS="$CITUS_CFLAGS -Werror=return-type"
 fi
 
+# Security flags
+# Flags taken from: https://liquid.microsoft.com/Web/Object/Read/ms.security/Requirements/Microsoft.Security.SystemsADM.10203#guide
+# We do not enforce the following flag because it is only available on GCC>=8
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CC supports -fstack-clash-protection" >&5
+$as_echo_n "checking whether $CC supports -fstack-clash-protection... " >&6; }
+if ${citusac_cv_prog_cc_cflags__fstack_clash_protection+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  citusac_save_CFLAGS=$CFLAGS
+flag=-fstack-clash-protection
+case $flag in -Wno*)
+	 flag=-W$(echo $flag | cut -c 6-)
+esac
+CFLAGS="$citusac_save_CFLAGS $flag"
+ac_save_c_werror_flag=$ac_c_werror_flag
+ac_c_werror_flag=yes
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  citusac_cv_prog_cc_cflags__fstack_clash_protection=yes
+else
+  citusac_cv_prog_cc_cflags__fstack_clash_protection=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+ac_c_werror_flag=$ac_save_c_werror_flag
+CFLAGS="$citusac_save_CFLAGS"
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $citusac_cv_prog_cc_cflags__fstack_clash_protection" >&5
+$as_echo "$citusac_cv_prog_cc_cflags__fstack_clash_protection" >&6; }
+if test x"$citusac_cv_prog_cc_cflags__fstack_clash_protection" = x"yes"; then
+  CITUS_CFLAGS="$CITUS_CFLAGS -fstack-clash-protection"
+fi
+
 
 #
 # --enable-coverage enables generation of code coverage metrics with gcov
@@ -4468,6 +4526,54 @@ cat >>confdefs.h <<_ACEOF
 _ACEOF
 
 
+
+
+
+# Check whether --with-security-flags was given.
+if test "${with_security_flags+set}" = set; then :
+  withval=$with_security_flags;
+  case $withval in
+    yes)
+      :
+      ;;
+    no)
+      :
+      ;;
+    *)
+      as_fn_error $? "no argument expected for --with-security-flags option" "$LINENO" 5
+      ;;
+  esac
+
+else
+  with_security_flags=no
+
+fi
+
+
+
+
+if test "$with_security_flags" = yes; then
+# Flags taken from: https://liquid.microsoft.com/Web/Object/Read/ms.security/Requirements/Microsoft.Security.SystemsADM.10203#guide
+
+# We always want to have some compiler flags for security concerns.
+SECURITY_CFLAGS="-fstack-protector-strong -D_FORTIFY_SOURCE=2 -O2 -z noexecstack -fpic -shared -Wl,-z,relro -Wl,-z,now -Wformat -Wformat-security -Werror=format-security"
+CITUS_CFLAGS="$CITUS_CFLAGS $SECURITY_CFLAGS"
+{ $as_echo "$as_me:${as_lineno-$LINENO}: Blindly added security flags for linker: $SECURITY_CFLAGS" >&5
+$as_echo "$as_me: Blindly added security flags for linker: $SECURITY_CFLAGS" >&6;}
+
+# We always want to have some clang flags for security concerns.
+# This doesn't include "-Wl,-z,relro -Wl,-z,now" on purpuse, because bitcode is not linked.
+# This doesn't include -fsanitize=cfi because it breaks builds on many distros including
+# Debian/Buster, Debian/Stretch, Ubuntu/Bionic, Ubuntu/Xenial and EL7.
+SECURITY_BITCODE_CFLAGS="-fsanitize=safe-stack -fstack-protector-strong -flto -fPIC -Wformat -Wformat-security -Werror=format-security"
+CITUS_BITCODE_CFLAGS="$CITUS_BITCODE_CFLAGS $SECURITY_BITCODE_CFLAGS"
+{ $as_echo "$as_me:${as_lineno-$LINENO}: Blindly added security flags for llvm: $SECURITY_BITCODE_CFLAGS" >&5
+$as_echo "$as_me: Blindly added security flags for llvm: $SECURITY_BITCODE_CFLAGS" >&6;}
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: If you run into issues during linking or bitcode compilation, you can use --without-security-flags." >&5
+$as_echo "$as_me: WARNING: If you run into issues during linking or bitcode compilation, you can use --without-security-flags." >&2;}
+fi
+
 # Check if git is installed, when installed the gitref of the checkout will be baked in the application
 # Extract the first word of "git", so it can be a program name with args.
 set dummy git; ac_word=$2
@@ -4533,6 +4639,8 @@ fi
 
 CITUS_CFLAGS="$CITUS_CFLAGS"
 
+CITUS_BITCODE_CFLAGS="$CITUS_BITCODE_CFLAGS"
+
 CITUS_CPPFLAGS="$CITUS_CPPFLAGS"
 
 CITUS_LDFLAGS="$LIBS $CITUS_LDFLAGS"
@@ -5055,7 +5163,7 @@ cat >>$CONFIG_STATUS <<\_ACEOF || ac_write_fail=1
 # report actual input values of CONFIG_FILES etc. instead of their
 # values after options handling.
 ac_log="
-This file was extended by Citus $as_me 9.5devel, which was
+This file was extended by Citus $as_me 9.5.12, which was
 generated by GNU Autoconf 2.69.  Invocation command line was
 
   CONFIG_FILES    = $CONFIG_FILES
@@ -5117,7 +5225,7 @@ _ACEOF
 cat >>$CONFIG_STATUS <<_ACEOF || ac_write_fail=1
 ac_cs_config="`$as_echo "$ac_configure_args" | sed 's/^ //; s/[\\""\`\$]/\\\\&/g'`"
 ac_cs_version="\\
-Citus config.status 9.5devel
+Citus config.status 9.5.12
 configured by $0, generated by GNU Autoconf 2.69,
   with options \\"\$ac_cs_config\\"
 

configure.in

@@ -5,7 +5,7 @@
 # everyone needing autoconf installed, the resulting files are checked
 # into the SCM.
 
-AC_INIT([Citus], [9.5devel])
+AC_INIT([Citus], [9.5.12])
 AC_COPYRIGHT([Copyright (c) Citus Data, Inc.])
 
 # we'll need sed and awk for some of the version commands
@@ -174,6 +174,10 @@ CITUSAC_PROG_CC_CFLAGS_OPT([-Werror=vla])  # visual studio does not support thes
 CITUSAC_PROG_CC_CFLAGS_OPT([-Werror=implicit-int])
 CITUSAC_PROG_CC_CFLAGS_OPT([-Werror=implicit-function-declaration])
 CITUSAC_PROG_CC_CFLAGS_OPT([-Werror=return-type])
+# Security flags
+# Flags taken from: https://liquid.microsoft.com/Web/Object/Read/ms.security/Requirements/Microsoft.Security.SystemsADM.10203#guide
+# We do not enforce the following flag because it is only available on GCC>=8
+CITUSAC_PROG_CC_CFLAGS_OPT([-fstack-clash-protection])
 
 #
 # --enable-coverage enables generation of code coverage metrics with gcov
@@ -212,11 +216,35 @@ PGAC_ARG_REQ(with, reports-hostname, [HOSTNAME],
 AC_DEFINE_UNQUOTED(REPORTS_BASE_URL, "$REPORTS_BASE_URL",
                    [Base URL for statistics collection and update checks])
 
+PGAC_ARG_BOOL(with, security-flags, no,
+              [use security flags])
+AC_SUBST(with_security_flags)
+
+if test "$with_security_flags" = yes; then
+# Flags taken from: https://liquid.microsoft.com/Web/Object/Read/ms.security/Requirements/Microsoft.Security.SystemsADM.10203#guide
+
+# We always want to have some compiler flags for security concerns.
+SECURITY_CFLAGS="-fstack-protector-strong -D_FORTIFY_SOURCE=2 -O2 -z noexecstack -fpic -shared -Wl,-z,relro -Wl,-z,now -Wformat -Wformat-security -Werror=format-security"
+CITUS_CFLAGS="$CITUS_CFLAGS $SECURITY_CFLAGS"
+AC_MSG_NOTICE([Blindly added security flags for linker: $SECURITY_CFLAGS])
+
+# We always want to have some clang flags for security concerns.
+# This doesn't include "-Wl,-z,relro -Wl,-z,now" on purpuse, because bitcode is not linked.
+# This doesn't include -fsanitize=cfi because it breaks builds on many distros including
+# Debian/Buster, Debian/Stretch, Ubuntu/Bionic, Ubuntu/Xenial and EL7.
+SECURITY_BITCODE_CFLAGS="-fsanitize=safe-stack -fstack-protector-strong -flto -fPIC -Wformat -Wformat-security -Werror=format-security"
+CITUS_BITCODE_CFLAGS="$CITUS_BITCODE_CFLAGS $SECURITY_BITCODE_CFLAGS"
+AC_MSG_NOTICE([Blindly added security flags for llvm: $SECURITY_BITCODE_CFLAGS])
+
+AC_MSG_WARN([If you run into issues during linking or bitcode compilation, you can use --without-security-flags.])
+fi
+
 # Check if git is installed, when installed the gitref of the checkout will be baked in the application
 AC_PATH_PROG(GIT_BIN, git)
 AC_CHECK_FILE(.git,[HAS_DOTGIT=yes], [HAS_DOTGIT=])
 
 AC_SUBST(CITUS_CFLAGS, "$CITUS_CFLAGS")
+AC_SUBST(CITUS_BITCODE_CFLAGS, "$CITUS_BITCODE_CFLAGS")
 AC_SUBST(CITUS_CPPFLAGS, "$CITUS_CPPFLAGS")
 AC_SUBST(CITUS_LDFLAGS, "$LIBS $CITUS_LDFLAGS")
 AC_SUBST(POSTGRES_SRCDIR, "$POSTGRES_SRCDIR")

src/backend/distributed/citus.control

@@ -1,6 +1,6 @@
 # Citus extension
 comment = 'Citus distributed database'
-default_version = '9.5-1'
+default_version = '9.5-3'
 module_pathname = '$libdir/citus'
 relocatable = false
 schema = pg_catalog

src/backend/distributed/commands/create_citus_local_table.c

@@ -569,7 +569,7 @@ ExecuteAndLogDDLCommand(const char *commandString)
 	ereport(DEBUG4, (errmsg("executing \"%s\"", commandString)));
 
 	Node *parseTree = ParseTreeNode(commandString);
-	CitusProcessUtility(parseTree, commandString, PROCESS_UTILITY_TOPLEVEL,
+	CitusProcessUtility(parseTree, commandString, PROCESS_UTILITY_QUERY,
 						NULL, None_Receiver, NULL);
 }
 

src/backend/distributed/commands/create_distributed_table.c

@@ -32,6 +32,7 @@
 #if PG_VERSION_NUM >= 12000
 #include "catalog/pg_proc.h"
 #endif
+#include "catalog/pg_rewrite_d.h"
 #include "catalog/pg_trigger.h"
 #include "commands/defrem.h"
 #include "commands/extension.h"
@@ -127,6 +128,8 @@ static void DoCopyFromLocalTableIntoShards(Relation distributedRelation,
 static void UndistributeTable(Oid relationId);
 static List * GetViewCreationCommandsOfTable(Oid relationId);
 static void ReplaceTable(Oid sourceId, Oid targetId);
+static void ErrorIfUnsupportedCascadeObjects(Oid relationId);
+static bool DoesCascadeDropUnsupportedObject(Oid classId, Oid id, HTAB *nodeMap);
 
 /* exports for SQL callable functions */
 PG_FUNCTION_INFO_V1(master_create_distributed_table);
@@ -368,6 +371,24 @@ CreateDistributedTable(Oid relationId, Var *distributionColumn, char distributio
 	char replicationModel = DecideReplicationModel(distributionMethod,
 												   viaDeprecatedAPI);
 
+
+	/*
+	 * Due to dropping columns, the parent's distribution key may not match the
+	 * partition's distribution key. The input distributionColumn belongs to
+	 * the parent. That's why we override the distribution column of partitions
+	 * here. See issue #5123 for details.
+	 */
+	if (PartitionTable(relationId))
+	{
+		Oid parentRelationId = PartitionParentOid(relationId);
+		char *distributionColumnName =
+			ColumnToColumnName(parentRelationId, nodeToString(distributionColumn));
+
+		distributionColumn =
+			FindColumnWithNameOnTargetRelation(parentRelationId, distributionColumnName,
+											   relationId);
+	}
+
 	/*
 	 * ColocationIdForNewTable assumes caller acquires lock on relationId. In our case,
 	 * our caller already acquired lock on relationId.
@@ -1601,6 +1622,8 @@ UndistributeTable(Oid relationId)
 								parentRelationName)));
 	}
 
+	ErrorIfUnsupportedCascadeObjects(relationId);
+
 	List *preLoadCommands = GetPreLoadTableCreationCommands(relationId, true);
 	List *postLoadCommands = GetPostLoadTableCreationCommands(relationId);
 
@@ -1658,7 +1681,7 @@ UndistributeTable(Oid relationId)
 		Node *parseTree = ParseTreeNode(tableCreationCommand);
 
 		RelayEventExtendNames(parseTree, schemaName, hashOfName);
-		CitusProcessUtility(parseTree, tableCreationCommand, PROCESS_UTILITY_TOPLEVEL,
+		CitusProcessUtility(parseTree, tableCreationCommand, PROCESS_UTILITY_QUERY,
 							NULL, None_Receiver, NULL);
 	}
 
@@ -1703,8 +1726,11 @@ GetViewCreationCommandsOfTable(Oid relationId)
 		char *viewName = get_rel_name(viewOid);
 		char *schemaName = get_namespace_name(get_rel_namespace(viewOid));
 		char *qualifiedViewName = quote_qualified_identifier(schemaName, viewName);
+		bool isMatView = get_rel_relkind(viewOid) == RELKIND_MATVIEW;
+
 		appendStringInfo(query,
-						 "CREATE VIEW %s AS %s",
+						 "CREATE %s VIEW %s AS %s",
+						 isMatView ? "MATERIALIZED" : "",
 						 qualifiedViewName,
 						 viewDefinition);
 		commands = lappend(commands, query->data);
@@ -1778,3 +1804,91 @@ ReplaceTable(Oid sourceId, Oid targetId)
 						   sourceName, false);
 #endif
 }
+
+
+/*
+ * ErrorIfUnsupportedCascadeObjects gets oid of a relation, finds the objects
+ * that dropping this relation cascades into and errors if there are any extensions
+ * that would be dropped.
+ */
+static void
+ErrorIfUnsupportedCascadeObjects(Oid relationId)
+{
+	HASHCTL info;
+	memset(&info, 0, sizeof(info));
+	info.keysize = sizeof(Oid);
+	info.entrysize = sizeof(Oid);
+	info.hash = oid_hash;
+	uint32 hashFlags = (HASH_ELEM | HASH_FUNCTION);
+	HTAB *nodeMap = hash_create("object dependency map (oid)", 64, &info, hashFlags);
+
+	bool unsupportedObjectInDepGraph =
+		DoesCascadeDropUnsupportedObject(RelationRelationId, relationId, nodeMap);
+
+	if (unsupportedObjectInDepGraph)
+	{
+		ereport(ERROR, (errmsg("cannot alter table because an extension depends on it")));
+	}
+}
+
+
+/*
+ * DoesCascadeDropUnsupportedObject walks through the objects that depend on the
+ * object with object id and returns true if it finds any unsupported objects.
+ *
+ * This function only checks extensions as unsupported objects.
+ *
+ * Extension dependency is different than the rest. If an object depends on an extension
+ * dropping the object would drop the extension too.
+ * So we check with IsObjectAddressOwnedByExtension function.
+ */
+static bool
+DoesCascadeDropUnsupportedObject(Oid classId, Oid objectId, HTAB *nodeMap)
+{
+	bool found = false;
+	hash_search(nodeMap, &objectId, HASH_ENTER, &found);
+
+	if (found)
+	{
+		return false;
+	}
+
+	ObjectAddress objectAddress = { 0 };
+	ObjectAddressSet(objectAddress, classId, objectId);
+
+	if (IsObjectAddressOwnedByExtension(&objectAddress, NULL))
+	{
+		return true;
+	}
+
+	Oid targetObjectClassId = classId;
+	Oid targetObjectId = objectId;
+	List *dependencyTupleList = GetPgDependTuplesForDependingObjects(targetObjectClassId,
+																	 targetObjectId);
+
+	HeapTuple depTup = NULL;
+	foreach_ptr(depTup, dependencyTupleList)
+	{
+		Form_pg_depend pg_depend = (Form_pg_depend) GETSTRUCT(depTup);
+
+		Oid dependingOid = InvalidOid;
+		Oid dependingClassId = InvalidOid;
+
+		if (pg_depend->classid == RewriteRelationId)
+		{
+			dependingOid = GetDependingView(pg_depend);
+			dependingClassId = RelationRelationId;
+		}
+		else
+		{
+			dependingOid = pg_depend->objid;
+			dependingClassId = pg_depend->classid;
+		}
+
+		if (DoesCascadeDropUnsupportedObject(dependingClassId, dependingOid, nodeMap))
+		{
+			return true;
+		}
+	}
+	return false;
+}

src/backend/distributed/commands/foreign_constraint.c

@@ -64,6 +64,8 @@ static void ForeignConstraintFindDistKeys(HeapTuple pgConstraintTuple,
 										  Var *referencedDistColumn,
 										  int *referencingAttrIndex,
 										  int *referencedAttrIndex);
+static List * GetForeignKeyIdsForColumn(char *columnName, Oid relationId,
+										int searchForeignKeyColumnFlags);
 static List * GetForeignConstraintCommandsInternal(Oid relationId, int flags);
 static Oid get_relation_constraint_oid_compat(HeapTuple heapTuple);
 static List * GetForeignKeyOidsToCitusLocalTables(Oid relationId);
@@ -483,6 +485,21 @@ ForeignConstraintFindDistKeys(HeapTuple pgConstraintTuple,
 }
 
 
+/*
+ * ColumnAppearsInForeignKey returns true if there is a foreign key constraint
+ * from/to given column. False otherwise.
+ */
+bool
+ColumnAppearsInForeignKey(char *columnName, Oid relationId)
+{
+	int searchForeignKeyColumnFlags = SEARCH_REFERENCING_RELATION |
+									  SEARCH_REFERENCED_RELATION;
+	List *foreignKeysColumnAppeared =
+		GetForeignKeyIdsForColumn(columnName, relationId, searchForeignKeyColumnFlags);
+	return list_length(foreignKeysColumnAppeared) > 0;
+}
+
+
 /*
  * ColumnAppearsInForeignKeyToReferenceTable checks if there is a foreign key
  * constraint from/to any reference table on the given column.
@@ -490,9 +507,45 @@ ForeignConstraintFindDistKeys(HeapTuple pgConstraintTuple,
 bool
 ColumnAppearsInForeignKeyToReferenceTable(char *columnName, Oid relationId)
 {
+	int searchForeignKeyColumnFlags = SEARCH_REFERENCING_RELATION |
+									  SEARCH_REFERENCED_RELATION;
+	List *foreignKeyIdsColumnAppeared =
+		GetForeignKeyIdsForColumn(columnName, relationId, searchForeignKeyColumnFlags);
+
+	Oid foreignKeyId = InvalidOid;
+	foreach_oid(foreignKeyId, foreignKeyIdsColumnAppeared)
+	{
+		Oid referencedTableId = GetReferencedTableId(foreignKeyId);
+		if (IsCitusTableType(referencedTableId, REFERENCE_TABLE))
+		{
+			return true;
+		}
+	}
+
+	return false;
+}
+
+
+/*
+ * GetForeignKeyIdsForColumn takes columnName and relationId for the owning
+ * relation, and returns a list of OIDs for foreign constraints that the column
+ * with columnName is involved according to "searchForeignKeyColumnFlags" argument.
+ * See SearchForeignKeyColumnFlags enum definition for usage.
+ */
+static List *
+GetForeignKeyIdsForColumn(char *columnName, Oid relationId,
+						  int searchForeignKeyColumnFlags)
+{
+	bool searchReferencing = searchForeignKeyColumnFlags & SEARCH_REFERENCING_RELATION;
+	bool searchReferenced = searchForeignKeyColumnFlags & SEARCH_REFERENCED_RELATION;
+
+	/* at least one of them should be true */
+	Assert(searchReferencing || searchReferenced);
+
+	List *foreignKeyIdsColumnAppeared = NIL;
+
 	ScanKeyData scanKey[1];
 	int scanKeyCount = 1;
-	bool foreignKeyToReferenceTableIncludesGivenColumn = false;
 
 	Relation pgConstraint = table_open(ConstraintRelationId, AccessShareLock);
 
@@ -511,11 +564,11 @@ ColumnAppearsInForeignKeyToReferenceTable(char *columnName, Oid relationId)
 		Oid referencedTableId = constraintForm->confrelid;
 		Oid referencingTableId = constraintForm->conrelid;
 
-		if (referencedTableId == relationId)
+		if (referencedTableId == relationId && searchReferenced)
 		{
 			pgConstraintKey = Anum_pg_constraint_confkey;
 		}
-		else if (referencingTableId == relationId)
+		else if (referencingTableId == relationId && searchReferencing)
 		{
 			pgConstraintKey = Anum_pg_constraint_conkey;
 		}
@@ -529,22 +582,12 @@ ColumnAppearsInForeignKeyToReferenceTable(char *columnName, Oid relationId)
 			continue;
 		}
 
-		/*
-		 * We check if the referenced table is a reference table. There cannot be
-		 * any foreign constraint from a distributed table to a local table.
-		 */
-		Assert(IsCitusTable(referencedTableId));
-		if (!IsCitusTableType(referencedTableId, REFERENCE_TABLE))
-		{
-			heapTuple = systable_getnext(scanDescriptor);
-			continue;
-		}
-
 		if (HeapTupleOfForeignConstraintIncludesColumn(heapTuple, relationId,
 													   pgConstraintKey, columnName))
 		{
-			foreignKeyToReferenceTableIncludesGivenColumn = true;
-			break;
+			Oid foreignKeyOid = get_relation_constraint_oid_compat(heapTuple);
+			foreignKeyIdsColumnAppeared = lappend_oid(foreignKeyIdsColumnAppeared,
+													  foreignKeyOid);
 		}
 
 		heapTuple = systable_getnext(scanDescriptor);
@@ -554,7 +597,7 @@ ColumnAppearsInForeignKeyToReferenceTable(char *columnName, Oid relationId)
 	systable_endscan(scanDescriptor);
 	table_close(pgConstraint, NoLock);
 
-	return foreignKeyToReferenceTableIncludesGivenColumn;
+	return foreignKeyIdsColumnAppeared;
 }
 
 
@@ -773,31 +816,70 @@ TableReferencing(Oid relationId)
 
 
 /*
- * ConstraintIsAForeignKey is a wrapper around GetForeignKeyOidByName that
- * returns true if the given constraint name identifies a foreign key
- * constraint defined on relation with relationId.
+ * ConstraintWithNameIsOfType is a wrapper around ConstraintWithNameIsOfType that returns true
+ * if given constraint name identifies a uniqueness constraint, i.e:
+ *   - primary key constraint, or
+ *   - unique constraint
  */
 bool
-ConstraintIsAForeignKey(char *inputConstaintName, Oid relationId)
+ConstraintIsAUniquenessConstraint(char *inputConstaintName, Oid relationId)
 {
-	Oid foreignKeyId = GetForeignKeyOidByName(inputConstaintName, relationId);
-	return OidIsValid(foreignKeyId);
+	bool isUniqueConstraint = ConstraintWithNameIsOfType(inputConstaintName, relationId,
+														 CONSTRAINT_UNIQUE);
+	bool isPrimaryConstraint = ConstraintWithNameIsOfType(inputConstaintName, relationId,
+														  CONSTRAINT_PRIMARY);
+	return isUniqueConstraint || isPrimaryConstraint;
 }
 
 
 /*
- * GetForeignKeyOidByName returns OID of the foreign key with name and defined
- * on relation with relationId. If there is no such foreign key constraint, then
- * this function returns InvalidOid.
+ * ConstraintIsAForeignKey is a wrapper around ConstraintWithNameIsOfType that returns true
+ * if given constraint name identifies a foreign key constraint.
  */
-Oid
-GetForeignKeyOidByName(char *inputConstaintName, Oid relationId)
+bool
+ConstraintIsAForeignKey(char *inputConstaintName, Oid relationId)
 {
-	int flags = INCLUDE_REFERENCING_CONSTRAINTS;
-	List *foreignKeyOids = GetForeignKeyOids(relationId, flags);
+	return ConstraintWithNameIsOfType(inputConstaintName, relationId, CONSTRAINT_FOREIGN);
+}
 
-	Oid foreignKeyId = FindForeignKeyOidWithName(foreignKeyOids, inputConstaintName);
-	return foreignKeyId;
+
+/*
+ * ConstraintWithNameIsOfType is a wrapper around get_relation_constraint_oid that
+ * returns true if given constraint name identifies a valid constraint defined
+ * on relation with relationId and it's type matches the input constraint type.
+ */
+bool
+ConstraintWithNameIsOfType(char *inputConstaintName, Oid relationId,
+						   char targetConstraintType)
+{
+	bool missingOk = true;
+	Oid constraintId =
+		get_relation_constraint_oid(relationId, inputConstaintName, missingOk);
+	return ConstraintWithIdIsOfType(constraintId, targetConstraintType);
+}
+
+
+/*
+ * ConstraintWithIdIsOfType returns true if constraint with constraintId exists
+ * and is of type targetConstraintType.
+ */
+bool
+ConstraintWithIdIsOfType(Oid constraintId, char targetConstraintType)
+{
+	HeapTuple heapTuple = SearchSysCache1(CONSTROID, ObjectIdGetDatum(constraintId));
+	if (!HeapTupleIsValid(heapTuple))
+	{
+		/* no such constraint */
+		return false;
+	}
+
+	Form_pg_constraint constraintForm = (Form_pg_constraint) GETSTRUCT(heapTuple);
+	char constraintType = constraintForm->contype;
+	bool constraintTypeMatches = (constraintType == targetConstraintType);
+
+	ReleaseSysCache(heapTuple);
+
+	return constraintTypeMatches;
 }
 
 

src/backend/distributed/commands/function.c

@@ -1138,12 +1138,16 @@ TriggerSyncMetadataToPrimaryNodes(void)
 
 			triggerMetadataSync = true;
 		}
+		else if (!workerNode->metadataSynced)
+		{
+			triggerMetadataSync = true;
+		}
 	}
 
 	/* let the maintanince deamon know about the metadata sync */
 	if (triggerMetadataSync)
 	{
-		TriggerMetadataSync(MyDatabaseId);
+		TriggerMetadataSyncOnCommit();
 	}
 }
 

src/backend/distributed/commands/index.c

@@ -511,6 +511,11 @@ PreprocessDropIndexStmt(Node *node, const char *dropIndexCommand)
 
 		ErrorIfUnsupportedDropIndexStmt(dropIndexStatement);
 
+		if (AnyForeignKeyDependsOnIndex(distributedIndexId))
+		{
+			MarkInvalidateForeignKeyGraph();
+		}
+
 		ddlJob->targetRelationId = distributedRelationId;
 		ddlJob->concurrentIndexCmd = dropIndexStatement->concurrent;
 

src/backend/distributed/commands/multi_copy.c

@@ -261,7 +261,8 @@ static CopyShardState * GetShardState(uint64 shardId, HTAB *shardStateHash,
 									  copyOutState, bool isCopyToIntermediateFile);
 static MultiConnection * CopyGetPlacementConnection(HTAB *connectionStateHash,
 													ShardPlacement *placement,
-													bool stopOnFailure);
+													bool stopOnFailure,
+													bool colocatedIntermediateResult);
 static bool HasReachedAdaptiveExecutorPoolSize(List *connectionStateHash);
 static MultiConnection * GetLeastUtilisedCopyConnection(List *connectionStateList,
 														char *nodeName, int nodePort);
@@ -2253,8 +2254,9 @@ CitusCopyDestReceiverStartup(DestReceiver *dest, int operation,
 
 	/* define the template for the COPY statement that is sent to workers */
 	CopyStmt *copyStatement = makeNode(CopyStmt);
-
-	if (copyDest->intermediateResultIdPrefix != NULL)
+	bool colocatedIntermediateResults =
+		copyDest->intermediateResultIdPrefix != NULL;
+	if (colocatedIntermediateResults)
 	{
 		copyStatement->relation = makeRangeVar(NULL, copyDest->intermediateResultIdPrefix,
 											   -1);
@@ -2291,13 +2293,21 @@ CitusCopyDestReceiverStartup(DestReceiver *dest, int operation,
 	RecordRelationAccessIfNonDistTable(tableId, PLACEMENT_ACCESS_DML);
 
 	/*
-	 * For all the primary (e.g., writable) nodes, reserve a shared connection.
-	 * We do this upfront because we cannot know which nodes are going to be
-	 * accessed. Since the order of the reservation is important, we need to
-	 * do it right here. For the details on why the order important, see
-	 * the function.
+	 * Colocated intermediate results do not honor citus.max_shared_pool_size,
+	 * so we don't need to reserve any connections. Each result file is sent
+	 * over a single connection.
 	 */
-	EnsureConnectionPossibilityForPrimaryNodes();
+	if (!colocatedIntermediateResults)
+	{
+		/*
+		 * For all the primary (e.g., writable) nodes, reserve a shared connection.
+		 * We do this upfront because we cannot know which nodes are going to be
+		 * accessed. Since the order of the reservation is important, we need to
+		 * do it right here. For the details on why the order important, see
+		 * the function.
+		 */
+		EnsureConnectionPossibilityForPrimaryNodes();
+	}
 }
 
 
@@ -3438,7 +3448,8 @@ InitializeCopyShardState(CopyShardState *shardState,
 		}
 
 		MultiConnection *connection =
-			CopyGetPlacementConnection(connectionStateHash, placement, stopOnFailure);
+			CopyGetPlacementConnection(connectionStateHash, placement, stopOnFailure,
+									   isCopyToIntermediateFile);
 		if (connection == NULL)
 		{
 			failedPlacementCount++;
@@ -3534,11 +3545,40 @@ LogLocalCopyExecution(uint64 shardId)
  * then it reuses the connection. Otherwise, it requests a connection for placement.
  */
 static MultiConnection *
-CopyGetPlacementConnection(HTAB *connectionStateHash, ShardPlacement *placement, bool
-						   stopOnFailure)
+CopyGetPlacementConnection(HTAB *connectionStateHash, ShardPlacement *placement,
+						   bool stopOnFailure, bool colocatedIntermediateResult)
 {
-	uint32 connectionFlags = FOR_DML;
-	char *nodeUser = CurrentUserName();
+	if (colocatedIntermediateResult)
+	{
+		/*
+		 * Colocated intermediate results are just files and not required to use
+		 * the same connections with their co-located shards. So, we are free to
+		 * use any connection we can get.
+		 *
+		 * Also, the current connection re-use logic does not know how to handle
+		 * intermediate results as the intermediate results always truncates the
+		 * existing files. That's why we we use one connection per intermediate
+		 * result.
+		 *
+		 * Also note that we are breaking the guarantees of citus.shared_pool_size
+		 * as we cannot rely on optional connections.
+		 */
+		uint32 connectionFlagsForIntermediateResult = 0;
+		MultiConnection *connection =
+			GetNodeConnection(connectionFlagsForIntermediateResult, placement->nodeName,
+							  placement->nodePort);
+
+		/*
+		 * As noted above, we want each intermediate file to go over
+		 * a separate connection.
+		 */
+		ClaimConnectionExclusively(connection);
+
+		/* and, we cannot afford to handle failures when anything goes wrong */
+		MarkRemoteTransactionCritical(connection);
+
+		return connection;
+	}
 
 	/*
 	 * Determine whether the task has to be assigned to a particular connection
@@ -3546,6 +3586,7 @@ CopyGetPlacementConnection(HTAB *connectionStateHash, ShardPlacement *placement,
 	 */
 	ShardPlacementAccess *placementAccess = CreatePlacementAccess(placement,
 																  PLACEMENT_ACCESS_DML);
+	uint32 connectionFlags = FOR_DML;
 	MultiConnection *connection =
 		GetConnectionIfPlacementAccessedInXact(connectionFlags,
 											   list_make1(placementAccess), NULL);
@@ -3583,6 +3624,12 @@ CopyGetPlacementConnection(HTAB *connectionStateHash, ShardPlacement *placement,
 													nodeName,
 													nodePort);
 
+		/*
+		 * Make sure that the connection management remembers that Citus
+		 * accesses this placement over the connection.
+		 */
+		AssignPlacementListToConnection(list_make1(placementAccess), connection);
+
 		return connection;
 	}
 
@@ -3628,6 +3675,7 @@ CopyGetPlacementConnection(HTAB *connectionStateHash, ShardPlacement *placement,
 		connectionFlags |= REQUIRE_CLEAN_CONNECTION;
 	}
 
+	char *nodeUser = CurrentUserName();
 	connection = GetPlacementConnection(connectionFlags, placement, nodeUser);
 	if (connection == NULL)
 	{
@@ -3643,6 +3691,12 @@ CopyGetPlacementConnection(HTAB *connectionStateHash, ShardPlacement *placement,
 			connection =
 				GetLeastUtilisedCopyConnection(copyConnectionStateList, nodeName,
 											   nodePort);
+
+			/*
+			 * Make sure that the connection management remembers that Citus
+			 * accesses this placement over the connection.
+			 */
+			AssignPlacementListToConnection(list_make1(placementAccess), connection);
 		}
 		else
 		{

src/backend/distributed/commands/table.c

@@ -17,6 +17,8 @@
 #include "access/xact.h"
 #include "catalog/index.h"
 #include "catalog/pg_class.h"
+#include "catalog/pg_constraint.h"
+#include "catalog/pg_depend.h"
 #include "commands/tablecmds.h"
 #include "distributed/citus_ruleutils.h"
 #include "distributed/colocation_utils.h"
@@ -24,9 +26,11 @@
 #include "distributed/commands/utility_hook.h"
 #include "distributed/deparser.h"
 #include "distributed/deparse_shard_query.h"
+#include "distributed/distribution_column.h"
 #include "distributed/listutils.h"
 #include "distributed/coordinator_protocol.h"
 #include "distributed/metadata_sync.h"
+#include "distributed/metadata/dependency.h"
 #include "distributed/multi_executor.h"
 #include "distributed/multi_partitioning_utils.h"
 #include "distributed/reference_table_utils.h"
@@ -49,6 +53,7 @@ static void ErrorIfAlterTableDefinesFKeyFromPostgresToCitusLocalTable(
 static List * GetAlterTableStmtFKeyConstraintList(AlterTableStmt *alterTableStatement);
 static List * GetAlterTableCommandFKeyConstraintList(AlterTableCmd *command);
 static bool AlterTableCommandTypeIsTrigger(AlterTableType alterTableType);
+static bool AlterTableDropsForeignKey(AlterTableStmt *alterTableStatement);
 static void ErrorIfUnsupportedAlterTableStmt(AlterTableStmt *alterTableStatement);
 static void ErrorIfCitusLocalTablePartitionCommand(AlterTableCmd *alterTableCmd,
 												   Oid parentRelationId);
@@ -384,6 +389,18 @@ PreprocessAlterTableStmt(Node *node, const char *alterTableCommand)
 	 */
 	ErrorIfAlterTableDefinesFKeyFromPostgresToCitusLocalTable(alterTableStatement);
 
+	if (AlterTableDropsForeignKey(alterTableStatement))
+	{
+		/*
+		 * The foreign key graph keeps track of the foreign keys including local tables.
+		 * So, even if a foreign key on a local table is dropped, we should invalidate
+		 * the graph so that the next commands can see the graph up-to-date.
+		 * We are aware that utility hook would still invalidate foreign key graph
+		 * even when command fails, but currently we are ok with that.
+		 */
+		MarkInvalidateForeignKeyGraph();
+	}
+
 	bool referencingIsLocalTable = !IsCitusTable(leftRelationId);
 	if (referencingIsLocalTable)
 	{
@@ -461,7 +478,9 @@ PreprocessAlterTableStmt(Node *node, const char *alterTableCommand)
 				 */
 				Assert(list_length(commandList) == 1);
 
-				Oid foreignKeyId = GetForeignKeyOidByName(constraintName, leftRelationId);
+				bool missingOk = false;
+				Oid foreignKeyId = get_relation_constraint_oid(leftRelationId,
+															   constraintName, missingOk);
 				rightRelationId = GetReferencedTableId(foreignKeyId);
 			}
 		}
@@ -714,6 +733,99 @@ AlterTableCommandTypeIsTrigger(AlterTableType alterTableType)
 }
 
 
+/*
+ * AlterTableDropsForeignKey returns true if the given AlterTableStmt drops
+ * a foreign key. False otherwise.
+ */
+static bool
+AlterTableDropsForeignKey(AlterTableStmt *alterTableStatement)
+{
+	LOCKMODE lockmode = AlterTableGetLockLevel(alterTableStatement->cmds);
+	Oid relationId = AlterTableLookupRelation(alterTableStatement, lockmode);
+
+	AlterTableCmd *command = NULL;
+	foreach_ptr(command, alterTableStatement->cmds)
+	{
+		AlterTableType alterTableType = command->subtype;
+
+		if (alterTableType == AT_DropColumn)
+		{
+			char *columnName = command->name;
+			if (ColumnAppearsInForeignKey(columnName, relationId))
+			{
+				/* dropping a column in the either side of the fkey will drop the fkey */
+				return true;
+			}
+		}
+
+		/*
+		 * In order to drop the foreign key, other than DROP COLUMN, the command must be
+		 * DROP CONSTRAINT command.
+		 */
+		if (alterTableType != AT_DropConstraint)
+		{
+			continue;
+		}
+
+		char *constraintName = command->name;
+		if (ConstraintIsAForeignKey(constraintName, relationId))
+		{
+			return true;
+		}
+		else if (ConstraintIsAUniquenessConstraint(constraintName, relationId))
+		{
+			/*
+			 * If the uniqueness constraint of the column that the foreign key depends on
+			 * is getting dropped, then the foreign key will also be dropped.
+			 */
+			bool missingOk = false;
+			Oid uniquenessConstraintId =
+				get_relation_constraint_oid(relationId, constraintName, missingOk);
+			Oid indexId = get_constraint_index(uniquenessConstraintId);
+			if (AnyForeignKeyDependsOnIndex(indexId))
+			{
+				return true;
+			}
+		}
+	}
+
+	return false;
+}
+
+
+/*
+ * AnyForeignKeyDependsOnIndex scans pg_depend and returns true if given index
+ * is valid and any foreign key depends on it.
+ */
+bool
+AnyForeignKeyDependsOnIndex(Oid indexId)
+{
+	Oid dependentObjectClassId = RelationRelationId;
+	Oid dependentObjectId = indexId;
+	List *dependencyTupleList =
+		GetPgDependTuplesForDependingObjects(dependentObjectClassId, dependentObjectId);
+
+	HeapTuple dependencyTuple = NULL;
+	foreach_ptr(dependencyTuple, dependencyTupleList)
+	{
+		Form_pg_depend dependencyForm = (Form_pg_depend) GETSTRUCT(dependencyTuple);
+		Oid dependingClassId = dependencyForm->classid;
+		if (dependingClassId != ConstraintRelationId)
+		{
+			continue;
+		}
+
+		Oid dependingObjectId = dependencyForm->objid;
+		if (ConstraintWithIdIsOfType(dependingObjectId, CONSTRAINT_FOREIGN))
+		{
+			return true;
+		}
+	}
+
+	return false;
+}
+
+
 /*
  * PreprocessAlterTableStmt issues a warning.
  * ALTER TABLE ALL IN TABLESPACE statements have their node type as
@@ -1339,21 +1451,6 @@ ErrorIfUnsupportedAlterTableStmt(AlterTableStmt *alterTableStatement)
 				break;
 			}
 
-			case AT_DropConstraint:
-			{
-				if (!OidIsValid(relationId))
-				{
-					return;
-				}
-
-				if (ConstraintIsAForeignKey(command->name, relationId))
-				{
-					MarkInvalidateForeignKeyGraph();
-				}
-
-				break;
-			}
-
 			case AT_EnableTrig:
 			case AT_EnableAlwaysTrig:
 			case AT_EnableReplicaTrig:
@@ -1383,6 +1480,7 @@ ErrorIfUnsupportedAlterTableStmt(AlterTableStmt *alterTableStatement)
 			case AT_SetNotNull:
 			case AT_ReplicaIdentity:
 			case AT_ValidateConstraint:
+			case AT_DropConstraint: /* we do the check for invalidation in AlterTableDropsForeignKey */
 			{
 				/*
 				 * We will not perform any special check for:

src/backend/distributed/connection/connection_management.c

@@ -161,6 +161,12 @@ AfterXactConnectionHandling(bool isCommit)
 	hash_seq_init(&status, ConnectionHash);
 	while ((entry = (ConnectionHashEntry *) hash_seq_search(&status)) != 0)
 	{
+		if (!entry->isValid)
+		{
+			/* skip invalid connection hash entries */
+			continue;
+		}
+
 		AfterXactHostConnectionHandling(entry, isCommit);
 
 		/*
@@ -289,11 +295,24 @@ StartNodeUserDatabaseConnection(uint32 flags, const char *hostname, int32 port,
 	 */
 
 	ConnectionHashEntry *entry = hash_search(ConnectionHash, &key, HASH_ENTER, &found);
-	if (!found)
+	if (!found || !entry->isValid)
 	{
+		/*
+		 * We are just building hash entry or previously it was left in an
+		 * invalid state as we couldn't allocate memory for it.
+		 * So initialize entry->connections list here.
+		 */
+		entry->isValid = false;
 		entry->connections = MemoryContextAlloc(ConnectionContext,
 												sizeof(dlist_head));
 		dlist_init(entry->connections);
+
+		/*
+		 * If MemoryContextAlloc errors out -e.g. during an OOM-, entry->connections
+		 * stays as NULL. So entry->isValid should be set to true right after we
+		 * initialize entry->connections properly.
+		 */
+		entry->isValid = true;
 	}
 
 	/* if desired, check whether there's a usable connection */
@@ -449,6 +468,12 @@ CloseAllConnectionsAfterTransaction(void)
 	hash_seq_init(&status, ConnectionHash);
 	while ((entry = (ConnectionHashEntry *) hash_seq_search(&status)) != 0)
 	{
+		if (!entry->isValid)
+		{
+			/* skip invalid connection hash entries */
+			continue;
+		}
+
 		dlist_iter iter;
 
 		dlist_head *connections = entry->connections;
@@ -483,7 +508,7 @@ ConnectionAvailableToNode(char *hostName, int nodePort, const char *userName,
 	ConnectionHashEntry *entry =
 		(ConnectionHashEntry *) hash_search(ConnectionHash, &key, HASH_FIND, &found);
 
-	if (!found)
+	if (!found || !entry->isValid)
 	{
 		return false;
 	}
@@ -509,6 +534,12 @@ CloseNodeConnectionsAfterTransaction(char *nodeName, int nodePort)
 	hash_seq_init(&status, ConnectionHash);
 	while ((entry = (ConnectionHashEntry *) hash_seq_search(&status)) != 0)
 	{
+		if (!entry->isValid)
+		{
+			/* skip invalid connection hash entries */
+			continue;
+		}
+
 		dlist_iter iter;
 
 		if (strcmp(entry->key.hostname, nodeName) != 0 || entry->key.port != nodePort)
@@ -584,6 +615,12 @@ ShutdownAllConnections(void)
 	hash_seq_init(&status, ConnectionHash);
 	while ((entry = (ConnectionHashEntry *) hash_seq_search(&status)) != NULL)
 	{
+		if (!entry->isValid)
+		{
+			/* skip invalid connection hash entries */
+			continue;
+		}
+
 		dlist_iter iter;
 
 		dlist_foreach(iter, entry->connections)
@@ -1194,6 +1231,12 @@ FreeConnParamsHashEntryFields(ConnParamsHashEntry *entry)
 static void
 AfterXactHostConnectionHandling(ConnectionHashEntry *entry, bool isCommit)
 {
+	if (!entry || !entry->isValid)
+	{
+		/* callers only pass valid hash entries but let's be on the safe side */
+		ereport(ERROR, (errmsg("connection hash entry is NULL or invalid")));
+	}
+
 	dlist_mutable_iter iter;
 	int cachedConnectionCount = 0;
 

src/backend/distributed/executor/adaptive_executor.c

@@ -174,6 +174,8 @@
 #include "utils/timestamp.h"
 
 #define SLOW_START_DISABLED 0
+#define WAIT_EVENT_SET_INDEX_NOT_INITIALIZED -1
+#define WAIT_EVENT_SET_INDEX_FAILED -2
 
 
 /*
@@ -611,6 +613,10 @@ static int UsableConnectionCount(WorkerPool *workerPool);
 static long NextEventTimeout(DistributedExecution *execution);
 static WaitEventSet * BuildWaitEventSet(List *sessionList);
 static void RebuildWaitEventSetFlags(WaitEventSet *waitEventSet, List *sessionList);
+static int CitusAddWaitEventSetToSet(WaitEventSet *set, uint32 events, pgsocket fd,
+									 Latch *latch, void *user_data);
+static bool CitusModifyWaitEvent(WaitEventSet *set, int pos, uint32 events,
+								 Latch *latch);
 static TaskPlacementExecution * PopPlacementExecution(WorkerSession *session);
 static TaskPlacementExecution * PopAssignedPlacementExecution(WorkerSession *session);
 static TaskPlacementExecution * PopUnassignedPlacementExecution(WorkerPool *workerPool);
@@ -642,6 +648,8 @@ static void ExtractParametersForRemoteExecution(ParamListInfo paramListInfo,
 												Oid **parameterTypes,
 												const char ***parameterValues);
 static int GetEventSetSize(List *sessionList);
+static bool ProcessSessionsWithFailedWaitEventSetOperations(
+	DistributedExecution *execution);
 static int RebuildWaitEventSet(DistributedExecution *execution);
 static void ProcessWaitEvents(DistributedExecution *execution, WaitEvent *events, int
 							  eventCount, bool *cancellationReceived);
@@ -660,6 +668,16 @@ static void SetAttributeInputMetadata(DistributedExecution *execution,
 void
 AdaptiveExecutorPreExecutorRun(CitusScanState *scanState)
 {
+	if (scanState->finishedPreScan)
+	{
+		/*
+		 * Cursors (and hence RETURN QUERY syntax in pl/pgsql functions)
+		 * may trigger AdaptiveExecutorPreExecutorRun() on every fetch
+		 * operation. Though, we should only execute PreScan once.
+		 */
+		return;
+	}
+
 	DistributedPlan *distributedPlan = scanState->distributedPlan;
 
 	/*
@@ -670,6 +688,8 @@ AdaptiveExecutorPreExecutorRun(CitusScanState *scanState)
 	LockPartitionsForDistributedPlan(distributedPlan);
 
 	ExecuteSubPlans(distributedPlan);
+
+	scanState->finishedPreScan = true;
 }
 
 
@@ -2084,6 +2104,7 @@ FindOrCreateWorkerSession(WorkerPool *workerPool, MultiConnection *connection)
 	session->connection = connection;
 	session->workerPool = workerPool;
 	session->commandsSent = 0;
+	session->waitEventSetIndex = WAIT_EVENT_SET_INDEX_NOT_INITIALIZED;
 
 	dlist_init(&session->pendingTaskQueue);
 	dlist_init(&session->readyTaskQueue);
@@ -2231,6 +2252,8 @@ RunDistributedExecution(DistributedExecution *execution)
 				ManageWorkerPool(workerPool);
 			}
 
+
+			bool skipWaitEvents = false;
 			if (execution->rebuildWaitEventSet)
 			{
 				if (events != NULL)
@@ -2245,11 +2268,28 @@ RunDistributedExecution(DistributedExecution *execution)
 				eventSetSize = RebuildWaitEventSet(execution);
 
 				events = palloc0(eventSetSize * sizeof(WaitEvent));
+
+				skipWaitEvents =
+					ProcessSessionsWithFailedWaitEventSetOperations(execution);
 			}
 			else if (execution->waitFlagsChanged)
 			{
 				RebuildWaitEventSetFlags(execution->waitEventSet, execution->sessionList);
 				execution->waitFlagsChanged = false;
+
+				skipWaitEvents =
+					ProcessSessionsWithFailedWaitEventSetOperations(execution);
+			}
+
+			if (skipWaitEvents)
+			{
+				/*
+				 * Some operation on the wait event set is failed, retry
+				 * as we already removed the problematic connections.
+				 */
+				execution->rebuildWaitEventSet = true;
+
+				continue;
 			}
 
 			/* wait for I/O events */
@@ -2297,6 +2337,51 @@ RunDistributedExecution(DistributedExecution *execution)
 }
 
 
+/*
+ * ProcessSessionsWithFailedEventSetOperations goes over the session list and
+ * processes sessions with failed wait event set operations.
+ *
+ * Failed sessions are not going to generate any further events, so it is our
+ * only chance to process the failure by calling into `ConnectionStateMachine`.
+ *
+ * The function returns true if any session failed.
+ */
+static bool
+ProcessSessionsWithFailedWaitEventSetOperations(DistributedExecution *execution)
+{
+	bool foundFailedSession = false;
+	WorkerSession *session = NULL;
+	foreach_ptr(session, execution->sessionList)
+	{
+		if (session->waitEventSetIndex == WAIT_EVENT_SET_INDEX_FAILED)
+		{
+			/*
+			 * We can only lost only already connected connections,
+			 * others are regular failures.
+			 */
+			MultiConnection *connection = session->connection;
+			if (connection->connectionState == MULTI_CONNECTION_CONNECTED)
+			{
+				connection->connectionState = MULTI_CONNECTION_LOST;
+			}
+			else
+			{
+				connection->connectionState = MULTI_CONNECTION_FAILED;
+			}
+
+
+			ConnectionStateMachine(session);
+
+			session->waitEventSetIndex = WAIT_EVENT_SET_INDEX_NOT_INITIALIZED;
+
+			foundFailedSession = true;
+		}
+	}
+
+	return foundFailedSession;
+}
+
+
 /*
  * RebuildWaitEventSet updates the waitEventSet for the distributed execution.
  * This happens when the connection set for the distributed execution is changed,
@@ -3285,6 +3370,25 @@ TransactionStateMachine(WorkerSession *session)
 			case REMOTE_TRANS_SENT_COMMAND:
 			{
 				TaskPlacementExecution *placementExecution = session->currentTask;
+				if (placementExecution == NULL)
+				{
+					/*
+					 * We have seen accounts in production where the placementExecution
+					 * could inadvertently be not set. Investigation documented on
+					 * https://github.com/citusdata/citus-enterprise/issues/493
+					 * (due to sensitive data in the initial report it is not discussed
+					 * in our community repository)
+					 *
+					 * Currently we don't have a reliable way of reproducing this issue.
+					 * Erroring here seems to be a more desirable approach compared to a
+					 * SEGFAULT on the dereference of placementExecution, with a possible
+					 * crash recovery as a result.
+					 */
+					ereport(ERROR, (errmsg(
+										"unable to recover from inconsistent state in "
+										"the connection state machine on coordinator")));
+				}
+
 				ShardCommandExecution *shardCommandExecution =
 					placementExecution->shardCommandExecution;
 				Task *task = shardCommandExecution->task;
@@ -3749,6 +3853,7 @@ ReceiveResults(WorkerSession *session, bool storeRows)
 		TupleDesc tupleDescriptor = tupleDest->tupleDescForQuery(tupleDest, queryIndex);
 		if (tupleDescriptor == NULL)
 		{
+			PQclear(result);
 			continue;
 		}
 
@@ -4455,18 +4560,79 @@ BuildWaitEventSet(List *sessionList)
 			continue;
 		}
 
-		int waitEventSetIndex = AddWaitEventToSet(waitEventSet, connection->waitFlags,
-												  sock, NULL, (void *) session);
+		int waitEventSetIndex =
+			CitusAddWaitEventSetToSet(waitEventSet, connection->waitFlags, sock,
+									  NULL, (void *) session);
 		session->waitEventSetIndex = waitEventSetIndex;
 	}
 
-	AddWaitEventToSet(waitEventSet, WL_POSTMASTER_DEATH, PGINVALID_SOCKET, NULL, NULL);
-	AddWaitEventToSet(waitEventSet, WL_LATCH_SET, PGINVALID_SOCKET, MyLatch, NULL);
+	CitusAddWaitEventSetToSet(waitEventSet, WL_POSTMASTER_DEATH, PGINVALID_SOCKET, NULL,
+							  NULL);
+	CitusAddWaitEventSetToSet(waitEventSet, WL_LATCH_SET, PGINVALID_SOCKET, MyLatch,
+							  NULL);
 
 	return waitEventSet;
 }
 
 
+/*
+ * CitusAddWaitEventSetToSet is a wrapper around Postgres' AddWaitEventToSet().
+ *
+ * AddWaitEventToSet() may throw hard errors. For example, when the
+ * underlying socket for a connection is closed by the remote server
+ * and already reflected by the OS, however Citus hasn't had a chance
+ * to get this information. In that case, if replication factor is >1,
+ * Citus can failover to other nodes for executing the query. Even if
+ * replication factor = 1, Citus can give much nicer errors.
+ *
+ * So CitusAddWaitEventSetToSet simply puts ModifyWaitEvent into a
+ * PG_TRY/PG_CATCH block in order to catch any hard errors, and
+ * returns this information to the caller.
+ */
+static int
+CitusAddWaitEventSetToSet(WaitEventSet *set, uint32 events, pgsocket fd,
+						  Latch *latch, void *user_data)
+{
+	volatile int waitEventSetIndex = WAIT_EVENT_SET_INDEX_NOT_INITIALIZED;
+	MemoryContext savedContext = CurrentMemoryContext;
+
+	PG_TRY();
+	{
+		waitEventSetIndex =
+			AddWaitEventToSet(set, events, fd, latch, (void *) user_data);
+	}
+	PG_CATCH();
+	{
+		/*
+		 * We might be in an arbitrary memory context when the
+		 * error is thrown and we should get back to one we had
+		 * at PG_TRY() time, especially because we are not
+		 * re-throwing the error.
+		 */
+		MemoryContextSwitchTo(savedContext);
+
+		FlushErrorState();
+
+		if (user_data != NULL)
+		{
+			WorkerSession *workerSession = (WorkerSession *) user_data;
+
+			ereport(DEBUG1, (errcode(ERRCODE_CONNECTION_FAILURE),
+							 errmsg("Adding wait event for node %s:%d failed. "
+									"The socket was: %d",
+									workerSession->workerPool->nodeName,
+									workerSession->workerPool->nodePort, fd)));
+		}
+
+		/* let the callers know about the failure */
+		waitEventSetIndex = WAIT_EVENT_SET_INDEX_FAILED;
+	}
+	PG_END_TRY();
+
+	return waitEventSetIndex;
+}
+
+
 /*
  * GetEventSetSize returns the event set size for a list of sessions.
  */
@@ -4510,11 +4676,68 @@ RebuildWaitEventSetFlags(WaitEventSet *waitEventSet, List *sessionList)
 			continue;
 		}
 
-		ModifyWaitEvent(waitEventSet, waitEventSetIndex, connection->waitFlags, NULL);
+		bool success =
+			CitusModifyWaitEvent(waitEventSet, waitEventSetIndex,
+								 connection->waitFlags, NULL);
+		if (!success)
+		{
+			ereport(DEBUG1, (errcode(ERRCODE_CONNECTION_FAILURE),
+							 errmsg("Modifying wait event for node %s:%d failed. "
+									"The wait event index was: %d",
+									connection->hostname, connection->port,
+									waitEventSetIndex)));
+
+			session->waitEventSetIndex = WAIT_EVENT_SET_INDEX_FAILED;
+		}
 	}
 }
 
 
+/*
+ * CitusModifyWaitEvent is a wrapper around Postgres' ModifyWaitEvent().
+ *
+ * ModifyWaitEvent may throw hard errors. For example, when the underlying
+ * socket for a connection is closed by the remote server and already
+ * reflected by the OS, however Citus hasn't had a chance to get this
+ * information. In that case, if repliction factor is >1, Citus can
+ * failover to other nodes for executing the query. Even if replication
+ * factor = 1, Citus can give much nicer errors.
+ *
+ * So CitusModifyWaitEvent simply puts ModifyWaitEvent into a PG_TRY/PG_CATCH
+ * block in order to catch any hard errors, and returns this information to the
+ * caller.
+ */
+static bool
+CitusModifyWaitEvent(WaitEventSet *set, int pos, uint32 events, Latch *latch)
+{
+	volatile bool success = true;
+	MemoryContext savedContext = CurrentMemoryContext;
+
+	PG_TRY();
+	{
+		ModifyWaitEvent(set, pos, events, latch);
+	}
+	PG_CATCH();
+	{
+		/*
+		 * We might be in an arbitrary memory context when the
+		 * error is thrown and we should get back to one we had
+		 * at PG_TRY() time, especially because we are not
+		 * re-throwing the error.
+		 */
+		MemoryContextSwitchTo(savedContext);
+
+		FlushErrorState();
+
+		/* let the callers know about the failure */
+		success = false;
+	}
+	PG_END_TRY();
+
+	return success;
+}
+
+
 /*
  * SetLocalForceMaxQueryParallelization is simply a C interface for setting
  * the following:

src/backend/distributed/executor/citus_custom_scan.c

@@ -300,7 +300,8 @@ CitusBeginReadOnlyScan(CustomScanState *node, EState *estate, int eflags)
 		 * The plan will be cached across executions when originalDistributedPlan
 		 * represents a prepared statement.
 		 */
-		CacheLocalPlanForShardQuery(task, originalDistributedPlan);
+		CacheLocalPlanForShardQuery(task, originalDistributedPlan,
+									estate->es_param_list_info);
 	}
 }
 
@@ -399,7 +400,8 @@ CitusBeginModifyScan(CustomScanState *node, EState *estate, int eflags)
 		 * The plan will be cached across executions when originalDistributedPlan
 		 * represents a prepared statement.
 		 */
-		CacheLocalPlanForShardQuery(task, originalDistributedPlan);
+		CacheLocalPlanForShardQuery(task, originalDistributedPlan,
+									estate->es_param_list_info);
 	}
 }
 
@@ -558,6 +560,9 @@ AdaptiveExecutorCreateScan(CustomScan *scan)
 	scanState->customScanState.methods = &AdaptiveExecutorCustomExecMethods;
 	scanState->PreExecScan = &CitusPreExecScan;
 
+	scanState->finishedPreScan = false;
+	scanState->finishedRemoteScan = false;
+
 	return (Node *) scanState;
 }
 
@@ -578,6 +583,9 @@ NonPushableInsertSelectCreateScan(CustomScan *scan)
 	scanState->customScanState.methods =
 		&NonPushableInsertSelectCustomExecMethods;
 
+	scanState->finishedPreScan = false;
+	scanState->finishedRemoteScan = false;
+
 	return (Node *) scanState;
 }
 

src/backend/distributed/executor/local_executor.c

@@ -124,9 +124,6 @@ static void LogLocalCommand(Task *task);
 static uint64 LocallyPlanAndExecuteMultipleQueries(List *queryStrings,
 												   TupleDestination *tupleDest,
 												   Task *task);
-static void ExtractParametersForLocalExecution(ParamListInfo paramListInfo,
-											   Oid **parameterTypes,
-											   const char ***parameterValues);
 static void LocallyExecuteUtilityTask(const char *utilityCommand);
 static void LocallyExecuteUdfTaskQuery(Query *localUdfCommandQuery);
 static void EnsureTransitionPossible(LocalExecutionStatus from,
@@ -362,7 +359,7 @@ LocallyPlanAndExecuteMultipleQueries(List *queryStrings, TupleDestination *tuple
  * value arrays. It does not change the oid of custom types, because the
  * query will be run locally.
  */
-static void
+void
 ExtractParametersForLocalExecution(ParamListInfo paramListInfo, Oid **parameterTypes,
 								   const char ***parameterValues)
 {
@@ -409,7 +406,8 @@ LocallyExecuteUtilityTask(const char *localTaskQueryCommand)
 			 * process utility.
 			 */
 			CitusProcessUtility(localTaskRawParseTree, localTaskQueryCommand,
-								PROCESS_UTILITY_TOPLEVEL, NULL, None_Receiver, NULL);
+								PROCESS_UTILITY_QUERY, NULL, None_Receiver,
+								NULL);
 		}
 	}
 }

src/backend/distributed/metadata/dependency.c

@@ -154,7 +154,6 @@ static void ApplyAddToDependencyList(ObjectAddressCollector *collector,
 static List * ExpandCitusSupportedTypes(ObjectAddressCollector *collector,
 										ObjectAddress target);
 static ViewDependencyNode * BuildViewDependencyGraph(Oid relationId, HTAB *nodeMap);
-static Oid GetDependingView(Form_pg_depend pg_depend);
 
 
 /*
@@ -1033,25 +1032,13 @@ BuildViewDependencyGraph(Oid relationId, HTAB *nodeMap)
 	node->remainingDependencyCount = 0;
 	node->dependingNodes = NIL;
 
-	ObjectAddress target = { 0 };
-	ObjectAddressSet(target, RelationRelationId, relationId);
+	Oid targetObjectClassId = RelationRelationId;
+	Oid targetObjectId = relationId;
+	List *dependencyTupleList = GetPgDependTuplesForDependingObjects(targetObjectClassId,
+																	 targetObjectId);
 
-	ScanKeyData key[2];
 	HeapTuple depTup = NULL;
-
-	/*
-	 * iterate the actual pg_depend catalog
-	 */
-	Relation depRel = table_open(DependRelationId, AccessShareLock);
-
-	ScanKeyInit(&key[0], Anum_pg_depend_refclassid, BTEqualStrategyNumber, F_OIDEQ,
-				ObjectIdGetDatum(target.classId));
-	ScanKeyInit(&key[1], Anum_pg_depend_refobjid, BTEqualStrategyNumber, F_OIDEQ,
-				ObjectIdGetDatum(target.objectId));
-	SysScanDesc depScan = systable_beginscan(depRel, DependReferenceIndexId,
-											 true, NULL, 2, key);
-
-	while (HeapTupleIsValid(depTup = systable_getnext(depScan)))
+	foreach_ptr(depTup, dependencyTupleList)
 	{
 		Form_pg_depend pg_depend = (Form_pg_depend) GETSTRUCT(depTup);
 
@@ -1066,13 +1053,48 @@ BuildViewDependencyGraph(Oid relationId, HTAB *nodeMap)
 		}
 	}
 
-	systable_endscan(depScan);
-	relation_close(depRel, AccessShareLock);
-
 	return node;
 }
 
 
+/*
+ * GetPgDependTuplesForDependingObjects scans pg_depend for given object and
+ * returns a list of heap tuples for the objects depending on it.
+ */
+List *
+GetPgDependTuplesForDependingObjects(Oid targetObjectClassId, Oid targetObjectId)
+{
+	List *dependencyTupleList = NIL;
+
+	Relation pgDepend = table_open(DependRelationId, AccessShareLock);
+
+	ScanKeyData key[2];
+	int scanKeyCount = 2;
+
+	ScanKeyInit(&key[0], Anum_pg_depend_refclassid, BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(targetObjectClassId));
+	ScanKeyInit(&key[1], Anum_pg_depend_refobjid, BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(targetObjectId));
+
+	bool useIndex = true;
+	SysScanDesc depScan = systable_beginscan(pgDepend, DependReferenceIndexId,
+											 useIndex, NULL, scanKeyCount, key);
+
+	HeapTuple dependencyTuple = NULL;
+	while (HeapTupleIsValid(dependencyTuple = systable_getnext(depScan)))
+	{
+		/* copy the tuple first */
+		dependencyTuple = heap_copytuple(dependencyTuple);
+		dependencyTupleList = lappend(dependencyTupleList, dependencyTuple);
+	}
+
+	systable_endscan(depScan);
+	relation_close(pgDepend, AccessShareLock);
+
+	return dependencyTupleList;
+}
+
+
 /*
  * GetDependingViews takes a relation id, finds the views that depend on the relation
  * and returns list of the oids of those views. It recurses on the pg_depend table to
@@ -1146,17 +1168,31 @@ GetDependingView(Form_pg_depend pg_depend)
 										   true, NULL, 1, rkey);
 
 	HeapTuple rewriteTup = systable_getnext(rscan);
+	if (!HeapTupleIsValid(rewriteTup))
+	{
+		/*
+		 * This function already verified that objid's classid is
+		 * RewriteRelationId, so it should exists. But be on the
+		 * safe side.
+		 */
+		ereport(ERROR, (errmsg("catalog lookup failed for view %u",
+							   pg_depend->objid)));
+	}
+
 	Form_pg_rewrite pg_rewrite = (Form_pg_rewrite) GETSTRUCT(rewriteTup);
 
 	bool isView = get_rel_relkind(pg_rewrite->ev_class) == RELKIND_VIEW;
+	bool isMatView = get_rel_relkind(pg_rewrite->ev_class) == RELKIND_MATVIEW;
 	bool isDifferentThanRef = pg_rewrite->ev_class != pg_depend->refobjid;
 
+	Oid dependingView = InvalidOid;
+	if ((isView || isMatView) && isDifferentThanRef)
+	{
+		dependingView = pg_rewrite->ev_class;
+	}
+
 	systable_endscan(rscan);
 	relation_close(rewriteRel, AccessShareLock);
 
-	if (isView && isDifferentThanRef)
-	{
-		return pg_rewrite->ev_class;
-	}
-	return InvalidOid;
+	return dependingView;
 }

src/backend/distributed/metadata/metadata_cache.c

@@ -254,8 +254,8 @@ static void InvalidateCitusTableCacheEntrySlot(CitusTableCacheEntrySlot *cacheSl
 static void InvalidateDistTableCache(void);
 static void InvalidateDistObjectCache(void);
 static void InitializeTableCacheEntry(int64 shardId);
-static bool IsCitusTableTypeInternal(CitusTableCacheEntry *tableEntry, CitusTableType
-									 tableType);
+static bool IsCitusTableTypeInternal(char partitionMethod, char replicationModel,
+									 CitusTableType tableType);
 static bool RefreshTableCacheEntryIfInvalid(ShardIdCacheEntry *shardEntry);
 
 
@@ -309,7 +309,7 @@ IsCitusTableType(Oid relationId, CitusTableType tableType)
 	{
 		return false;
 	}
-	return IsCitusTableTypeInternal(tableEntry, tableType);
+	return IsCitusTableTypeCacheEntry(tableEntry, tableType);
 }
 
 
@@ -320,7 +320,8 @@ IsCitusTableType(Oid relationId, CitusTableType tableType)
 bool
 IsCitusTableTypeCacheEntry(CitusTableCacheEntry *tableEntry, CitusTableType tableType)
 {
-	return IsCitusTableTypeInternal(tableEntry, tableType);
+	return IsCitusTableTypeInternal(tableEntry->partitionMethod,
+									tableEntry->replicationModel, tableType);
 }
 
 
@@ -329,47 +330,48 @@ IsCitusTableTypeCacheEntry(CitusTableCacheEntry *tableEntry, CitusTableType tabl
  * the given table type group. For definition of table types, see CitusTableType.
  */
 static bool
-IsCitusTableTypeInternal(CitusTableCacheEntry *tableEntry, CitusTableType tableType)
+IsCitusTableTypeInternal(char partitionMethod, char replicationModel,
+						 CitusTableType tableType)
 {
 	switch (tableType)
 	{
 		case HASH_DISTRIBUTED:
 		{
-			return tableEntry->partitionMethod == DISTRIBUTE_BY_HASH;
+			return partitionMethod == DISTRIBUTE_BY_HASH;
 		}
 
 		case APPEND_DISTRIBUTED:
 		{
-			return tableEntry->partitionMethod == DISTRIBUTE_BY_APPEND;
+			return partitionMethod == DISTRIBUTE_BY_APPEND;
 		}
 
 		case RANGE_DISTRIBUTED:
 		{
-			return tableEntry->partitionMethod == DISTRIBUTE_BY_RANGE;
+			return partitionMethod == DISTRIBUTE_BY_RANGE;
 		}
 
 		case DISTRIBUTED_TABLE:
 		{
-			return tableEntry->partitionMethod == DISTRIBUTE_BY_HASH ||
-				   tableEntry->partitionMethod == DISTRIBUTE_BY_RANGE ||
-				   tableEntry->partitionMethod == DISTRIBUTE_BY_APPEND;
+			return partitionMethod == DISTRIBUTE_BY_HASH ||
+				   partitionMethod == DISTRIBUTE_BY_RANGE ||
+				   partitionMethod == DISTRIBUTE_BY_APPEND;
 		}
 
 		case REFERENCE_TABLE:
 		{
-			return tableEntry->partitionMethod == DISTRIBUTE_BY_NONE &&
-				   tableEntry->replicationModel == REPLICATION_MODEL_2PC;
+			return partitionMethod == DISTRIBUTE_BY_NONE &&
+				   replicationModel == REPLICATION_MODEL_2PC;
 		}
 
 		case CITUS_LOCAL_TABLE:
 		{
-			return tableEntry->partitionMethod == DISTRIBUTE_BY_NONE &&
-				   tableEntry->replicationModel != REPLICATION_MODEL_2PC;
+			return partitionMethod == DISTRIBUTE_BY_NONE &&
+				   replicationModel != REPLICATION_MODEL_2PC;
 		}
 
 		case CITUS_TABLE_WITH_NO_DIST_KEY:
 		{
-			return tableEntry->partitionMethod == DISTRIBUTE_BY_NONE;
+			return partitionMethod == DISTRIBUTE_BY_NONE;
 		}
 
 		case ANY_CITUS_TABLE_TYPE:
@@ -3706,12 +3708,25 @@ CitusTableTypeIdList(CitusTableType citusTableType)
 	while (HeapTupleIsValid(heapTuple))
 	{
 		bool isNull = false;
-		Datum relationIdDatum = heap_getattr(heapTuple,
-											 Anum_pg_dist_partition_logicalrelid,
-											 tupleDescriptor, &isNull);
-		Oid relationId = DatumGetObjectId(relationIdDatum);
-		if (IsCitusTableType(relationId, citusTableType))
+
+		Datum partMethodDatum =
+			heap_getattr(heapTuple, Anum_pg_dist_partition_partmethod,
+						 tupleDescriptor, &isNull);
+		Datum replicationModelDatum =
+			heap_getattr(heapTuple, Anum_pg_dist_partition_repmodel,
+						 tupleDescriptor, &isNull);
+
+		Oid partitionMethod = DatumGetChar(partMethodDatum);
+		Oid replicationModel = DatumGetChar(replicationModelDatum);
+
+		if (IsCitusTableTypeInternal(partitionMethod, replicationModel, citusTableType))
 		{
+			Datum relationIdDatum = heap_getattr(heapTuple,
+												 Anum_pg_dist_partition_logicalrelid,
+												 tupleDescriptor, &isNull);
+
+			Oid relationId = DatumGetObjectId(relationIdDatum);
+
 			relationIdList = lappend_oid(relationIdList, relationId);
 		}
 

src/backend/distributed/metadata/metadata_sync.c

@@ -14,6 +14,7 @@
 #include "postgres.h"
 #include "miscadmin.h"
 
+#include <signal.h>
 #include <sys/stat.h>
 #include <unistd.h>
 
@@ -28,6 +29,7 @@
 #include "catalog/pg_foreign_server.h"
 #include "catalog/pg_namespace.h"
 #include "catalog/pg_type.h"
+#include "commands/async.h"
 #include "distributed/citus_ruleutils.h"
 #include "distributed/commands.h"
 #include "distributed/deparser.h"
@@ -35,6 +37,7 @@
 #include "distributed/listutils.h"
 #include "distributed/metadata_utility.h"
 #include "distributed/coordinator_protocol.h"
+#include "distributed/maintenanced.h"
 #include "distributed/metadata_cache.h"
 #include "distributed/metadata_sync.h"
 #include "distributed/metadata/distobject.h"
@@ -48,11 +51,15 @@
 #include "foreign/foreign.h"
 #include "miscadmin.h"
 #include "nodes/pg_list.h"
+#include "pgstat.h"
+#include "postmaster/bgworker.h"
+#include "postmaster/postmaster.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
 #include "utils/fmgroids.h"
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
+#include "utils/snapmgr.h"
 #include "utils/syscache.h"
 
 
@@ -76,11 +83,18 @@ static GrantStmt * GenerateGrantOnSchemaStmtForRights(Oid roleOid,
 													  char *permission,
 													  bool withGrantOption);
 static char * GenerateSetRoleQuery(Oid roleOid);
+static void MetadataSyncSigTermHandler(SIGNAL_ARGS);
+static void MetadataSyncSigAlrmHandler(SIGNAL_ARGS);
 
 PG_FUNCTION_INFO_V1(start_metadata_sync_to_node);
 PG_FUNCTION_INFO_V1(stop_metadata_sync_to_node);
 PG_FUNCTION_INFO_V1(worker_record_sequence_dependency);
 
+static bool got_SIGTERM = false;
+static bool got_SIGALRM = false;
+
+#define METADATA_SYNC_APP_NAME "Citus Metadata Sync Daemon"
+
 
 /*
  * start_metadata_sync_to_node function sets hasmetadata column of the given
@@ -1481,7 +1495,7 @@ DetachPartitionCommandList(void)
  * metadata workers that are out of sync. Returns the result of
  * synchronization.
  */
-MetadataSyncResult
+static MetadataSyncResult
 SyncMetadataToNodes(void)
 {
 	MetadataSyncResult result = METADATA_SYNC_SUCCESS;
@@ -1511,6 +1525,9 @@ SyncMetadataToNodes(void)
 
 			if (!SyncMetadataSnapshotToNode(workerNode, raiseInterrupts))
 			{
+				ereport(WARNING, (errmsg("failed to sync metadata to %s:%d",
+										 workerNode->workerName,
+										 workerNode->workerPort)));
 				result = METADATA_SYNC_FAILED_SYNC;
 			}
 			else
@@ -1523,3 +1540,244 @@ SyncMetadataToNodes(void)
 
 	return result;
 }
+
+
+/*
+ * SyncMetadataToNodesMain is the main function for syncing metadata to
+ * MX nodes. It retries until success and then exits.
+ */
+void
+SyncMetadataToNodesMain(Datum main_arg)
+{
+	Oid databaseOid = DatumGetObjectId(main_arg);
+
+	/* extension owner is passed via bgw_extra */
+	Oid extensionOwner = InvalidOid;
+	memcpy_s(&extensionOwner, sizeof(extensionOwner),
+			 MyBgworkerEntry->bgw_extra, sizeof(Oid));
+
+	pqsignal(SIGTERM, MetadataSyncSigTermHandler);
+	pqsignal(SIGALRM, MetadataSyncSigAlrmHandler);
+	BackgroundWorkerUnblockSignals();
+
+	/* connect to database, after that we can actually access catalogs */
+	BackgroundWorkerInitializeConnectionByOid(databaseOid, extensionOwner, 0);
+
+	/* make worker recognizable in pg_stat_activity */
+	pgstat_report_appname(METADATA_SYNC_APP_NAME);
+
+	bool syncedAllNodes = false;
+
+	while (!syncedAllNodes)
+	{
+		InvalidateMetadataSystemCache();
+		StartTransactionCommand();
+
+		/*
+		 * Some functions in ruleutils.c, which we use to get the DDL for
+		 * metadata propagation, require an active snapshot.
+		 */
+		PushActiveSnapshot(GetTransactionSnapshot());
+
+		if (!LockCitusExtension())
+		{
+			ereport(DEBUG1, (errmsg("could not lock the citus extension, "
+									"skipping metadata sync")));
+		}
+		else if (CheckCitusVersion(DEBUG1) && CitusHasBeenLoaded())
+		{
+			UseCoordinatedTransaction();
+			MetadataSyncResult result = SyncMetadataToNodes();
+
+			syncedAllNodes = (result == METADATA_SYNC_SUCCESS);
+
+			/* we use LISTEN/NOTIFY to wait for metadata syncing in tests */
+			if (result != METADATA_SYNC_FAILED_LOCK)
+			{
+				Async_Notify(METADATA_SYNC_CHANNEL, NULL);
+			}
+		}
+
+		PopActiveSnapshot();
+		CommitTransactionCommand();
+		ProcessCompletedNotifies();
+
+		if (syncedAllNodes)
+		{
+			break;
+		}
+
+		/*
+		 * If backend is cancelled (e.g. bacause of distributed deadlock),
+		 * CHECK_FOR_INTERRUPTS() will raise a cancellation error which will
+		 * result in exit(1).
+		 */
+		CHECK_FOR_INTERRUPTS();
+
+		/*
+		 * SIGTERM is used for when maintenance daemon tries to clean-up
+		 * metadata sync daemons spawned by terminated maintenance daemons.
+		 */
+		if (got_SIGTERM)
+		{
+			exit(0);
+		}
+
+		/*
+		 * SIGALRM is used for testing purposes and it simulates an error in metadata
+		 * sync daemon.
+		 */
+		if (got_SIGALRM)
+		{
+			elog(ERROR, "Error in metadata sync daemon");
+		}
+
+		pg_usleep(MetadataSyncRetryInterval * 1000);
+	}
+}
+
+
+/*
+ * MetadataSyncSigTermHandler set a flag to request termination of metadata
+ * sync daemon.
+ */
+static void
+MetadataSyncSigTermHandler(SIGNAL_ARGS)
+{
+	int save_errno = errno;
+
+	got_SIGTERM = true;
+	if (MyProc != NULL)
+	{
+		SetLatch(&MyProc->procLatch);
+	}
+
+	errno = save_errno;
+}
+
+
+/*
+ * MetadataSyncSigAlrmHandler set a flag to request error at metadata
+ * sync daemon. This is used for testing purposes.
+ */
+static void
+MetadataSyncSigAlrmHandler(SIGNAL_ARGS)
+{
+	int save_errno = errno;
+
+	got_SIGALRM = true;
+	if (MyProc != NULL)
+	{
+		SetLatch(&MyProc->procLatch);
+	}
+
+	errno = save_errno;
+}
+
+
+/*
+ * SpawnSyncMetadataToNodes starts a background worker which runs metadata
+ * sync. On success it returns workers' handle. Otherwise it returns NULL.
+ */
+BackgroundWorkerHandle *
+SpawnSyncMetadataToNodes(Oid database, Oid extensionOwner)
+{
+	BackgroundWorker worker;
+	BackgroundWorkerHandle *handle = NULL;
+
+	/* Configure a worker. */
+	memset(&worker, 0, sizeof(worker));
+	SafeSnprintf(worker.bgw_name, BGW_MAXLEN,
+				 "Citus Metadata Sync: %u/%u",
+				 database, extensionOwner);
+	worker.bgw_flags =
+		BGWORKER_SHMEM_ACCESS | BGWORKER_BACKEND_DATABASE_CONNECTION;
+	worker.bgw_start_time = BgWorkerStart_ConsistentState;
+
+	/* don't restart, we manage restarts from maintenance daemon */
+	worker.bgw_restart_time = BGW_NEVER_RESTART;
+	strcpy_s(worker.bgw_library_name, sizeof(worker.bgw_library_name), "citus");
+	strcpy_s(worker.bgw_function_name, sizeof(worker.bgw_library_name),
+			 "SyncMetadataToNodesMain");
+	worker.bgw_main_arg = ObjectIdGetDatum(MyDatabaseId);
+	memcpy_s(worker.bgw_extra, sizeof(worker.bgw_extra), &extensionOwner,
+			 sizeof(Oid));
+	worker.bgw_notify_pid = MyProcPid;
+
+	if (!RegisterDynamicBackgroundWorker(&worker, &handle))
+	{
+		return NULL;
+	}
+
+	pid_t pid;
+	WaitForBackgroundWorkerStartup(handle, &pid);
+
+	return handle;
+}
+
+
+/*
+ * SignalMetadataSyncDaemon signals metadata sync daemons belonging to
+ * the given database.
+ */
+void
+SignalMetadataSyncDaemon(Oid database, int sig)
+{
+	int backendCount = pgstat_fetch_stat_numbackends();
+	for (int backend = 1; backend <= backendCount; backend++)
+	{
+		LocalPgBackendStatus *localBeEntry = pgstat_fetch_stat_local_beentry(backend);
+		if (!localBeEntry)
+		{
+			continue;
+		}
+
+		PgBackendStatus *beStatus = &localBeEntry->backendStatus;
+		if (beStatus->st_databaseid == database &&
+			strncmp(beStatus->st_appname, METADATA_SYNC_APP_NAME, BGW_MAXLEN) == 0)
+		{
+			kill(beStatus->st_procpid, sig);
+		}
+	}
+}
+
+
+/*
+ * ShouldInitiateMetadataSync returns if metadata sync daemon should be initiated.
+ * It sets lockFailure to true if pg_dist_node lock couldn't be acquired for the
+ * check.
+ */
+bool
+ShouldInitiateMetadataSync(bool *lockFailure)
+{
+	if (!IsCoordinator())
+	{
+		*lockFailure = false;
+		return false;
+	}
+
+	Oid distNodeOid = DistNodeRelationId();
+	if (!ConditionalLockRelationOid(distNodeOid, AccessShareLock))
+	{
+		*lockFailure = true;
+		return false;
+	}
+
+	bool shouldSyncMetadata = false;
+
+	List *workerList = ActivePrimaryNonCoordinatorNodeList(NoLock);
+	WorkerNode *workerNode = NULL;
+	foreach_ptr(workerNode, workerList)
+	{
+		if (workerNode->hasMetadata && !workerNode->metadataSynced)
+		{
+			shouldSyncMetadata = true;
+			break;
+		}
+	}
+
+	UnlockRelationOid(distNodeOid, AccessShareLock);
+
+	*lockFailure = false;
+	return shouldSyncMetadata;
+}

src/backend/distributed/metadata/metadata_utility.c

@@ -35,6 +35,7 @@
 #include "distributed/citus_nodes.h"
 #include "distributed/citus_safe_lib.h"
 #include "distributed/listutils.h"
+#include "distributed/lock_graph.h"
 #include "distributed/metadata_utility.h"
 #include "distributed/coordinator_protocol.h"
 #include "distributed/metadata_cache.h"
@@ -50,6 +51,7 @@
 #include "distributed/relay_utility.h"
 #include "distributed/resource_lock.h"
 #include "distributed/remote_commands.h"
+#include "distributed/tuplestore.h"
 #include "distributed/worker_manager.h"
 #include "distributed/worker_protocol.h"
 #include "distributed/version_compat.h"
@@ -75,9 +77,23 @@ static uint64 DistributedTableSize(Oid relationId, char *sizeQuery);
 static uint64 DistributedTableSizeOnWorker(WorkerNode *workerNode, Oid relationId,
 										   char *sizeQuery);
 static List * ShardIntervalsOnWorkerGroup(WorkerNode *workerNode, Oid relationId);
+static char * GenerateShardStatisticsQueryForShardList(List *shardIntervalList, bool
+													   useShardMinMaxQuery);
+static char * GenerateAllShardStatisticsQueryForNode(WorkerNode *workerNode,
+													 List *citusTableIds, bool
+													 useShardMinMaxQuery);
+static List * GenerateShardStatisticsQueryList(List *workerNodeList, List *citusTableIds,
+											   bool useShardMinMaxQuery);
 static void ErrorIfNotSuitableToGetSize(Oid relationId);
 static ShardPlacement * ShardPlacementOnGroup(uint64 shardId, int groupId);
 
+static List * OpenConnectionToNodes(List *workerNodeList);
+static void AppendShardSizeMinMaxQuery(StringInfo selectQuery, uint64 shardId,
+									   ShardInterval *
+									   shardInterval, char *shardName,
+									   char *quotedShardName);
+static void AppendShardSizeQuery(StringInfo selectQuery, ShardInterval *shardInterval,
+								 char *quotedShardName);
 
 /* exports for SQL callable functions */
 PG_FUNCTION_INFO_V1(citus_table_size);
@@ -154,6 +170,106 @@ citus_relation_size(PG_FUNCTION_ARGS)
 }
 
 
+/*
+ * SendShardStatisticsQueriesInParallel generates query lists for obtaining shard
+ * statistics and then sends the commands in parallel by opening connections
+ * to available nodes. It returns the connection list.
+ */
+List *
+SendShardStatisticsQueriesInParallel(List *citusTableIds, bool useDistributedTransaction,
+									 bool
+									 useShardMinMaxQuery)
+{
+	List *workerNodeList = ActivePrimaryNodeList(NoLock);
+
+	List *shardSizesQueryList = GenerateShardStatisticsQueryList(workerNodeList,
+																 citusTableIds,
+																 useShardMinMaxQuery);
+
+	List *connectionList = OpenConnectionToNodes(workerNodeList);
+	FinishConnectionListEstablishment(connectionList);
+
+	if (useDistributedTransaction)
+	{
+		/*
+		 * For now, in the case we want to include shard min and max values, we also
+		 * want to update the entries in pg_dist_placement and pg_dist_shard with the
+		 * latest statistics. In order to detect distributed deadlocks, we assign a
+		 * distributed transaction ID to the current transaction
+		 */
+		UseCoordinatedTransaction();
+	}
+
+	/* send commands in parallel */
+	for (int i = 0; i < list_length(connectionList); i++)
+	{
+		MultiConnection *connection = (MultiConnection *) list_nth(connectionList, i);
+		char *shardSizesQuery = (char *) list_nth(shardSizesQueryList, i);
+
+		if (useDistributedTransaction)
+		{
+			/* run the size query in a distributed transaction */
+			RemoteTransactionBeginIfNecessary(connection);
+		}
+
+		int querySent = SendRemoteCommand(connection, shardSizesQuery);
+
+		if (querySent == 0)
+		{
+			ReportConnectionError(connection, WARNING);
+		}
+	}
+	return connectionList;
+}
+
+
+/*
+ * OpenConnectionToNodes opens a single connection per node
+ * for the given workerNodeList.
+ */
+static List *
+OpenConnectionToNodes(List *workerNodeList)
+{
+	List *connectionList = NIL;
+	WorkerNode *workerNode = NULL;
+	foreach_ptr(workerNode, workerNodeList)
+	{
+		const char *nodeName = workerNode->workerName;
+		int nodePort = workerNode->workerPort;
+		int connectionFlags = 0;
+
+		MultiConnection *connection = StartNodeConnection(connectionFlags, nodeName,
+														  nodePort);
+
+		connectionList = lappend(connectionList, connection);
+	}
+	return connectionList;
+}
+
+
+/*
+ * GenerateShardStatisticsQueryList generates a query per node that will return:
+ * - all shard_name, shard_size pairs from the node (if includeShardMinMax is false)
+ * - all shard_id, shard_minvalue, shard_maxvalue, shard_size quartuples from the node (if true)
+ */
+static List *
+GenerateShardStatisticsQueryList(List *workerNodeList, List *citusTableIds, bool
+								 useShardMinMaxQuery)
+{
+	List *shardStatisticsQueryList = NIL;
+	WorkerNode *workerNode = NULL;
+	foreach_ptr(workerNode, workerNodeList)
+	{
+		char *shardStatisticsQuery = GenerateAllShardStatisticsQueryForNode(workerNode,
+																			citusTableIds,
+																			useShardMinMaxQuery);
+		shardStatisticsQueryList = lappend(shardStatisticsQueryList,
+										   shardStatisticsQuery);
+	}
+	return shardStatisticsQueryList;
+}
+
+
 /*
  * DistributedTableSize is helper function for each kind of citus size functions.
  * It first checks whether the table is distributed and size query can be run on
@@ -352,6 +468,130 @@ GenerateSizeQueryOnMultiplePlacements(List *shardIntervalList, char *sizeQuery)
 }
 
 
+/*
+ * GenerateAllShardStatisticsQueryForNode generates a query that returns:
+ * - all shard_name, shard_size pairs for the given node (if useShardMinMaxQuery is false)
+ * - all shard_id, shard_minvalue, shard_maxvalue, shard_size quartuples (if true)
+ */
+static char *
+GenerateAllShardStatisticsQueryForNode(WorkerNode *workerNode, List *citusTableIds, bool
+									   useShardMinMaxQuery)
+{
+	StringInfo allShardStatisticsQuery = makeStringInfo();
+
+	Oid relationId = InvalidOid;
+	foreach_oid(relationId, citusTableIds)
+	{
+		List *shardIntervalsOnNode = ShardIntervalsOnWorkerGroup(workerNode, relationId);
+		char *shardStatisticsQuery =
+			GenerateShardStatisticsQueryForShardList(shardIntervalsOnNode,
+													 useShardMinMaxQuery);
+		appendStringInfoString(allShardStatisticsQuery, shardStatisticsQuery);
+	}
+
+	/* Add a dummy entry so that UNION ALL doesn't complain */
+	if (useShardMinMaxQuery)
+	{
+		/* 0 for shard_id, NULL for min, NULL for text, 0 for shard_size */
+		appendStringInfo(allShardStatisticsQuery,
+						 "SELECT 0::bigint, NULL::text, NULL::text, 0::bigint;");
+	}
+	else
+	{
+		/* NULL for shard_name, 0 for shard_size */
+		appendStringInfo(allShardStatisticsQuery, "SELECT NULL::text, 0::bigint;");
+	}
+	return allShardStatisticsQuery->data;
+}
+
+
+/*
+ * GenerateShardStatisticsQueryForShardList generates one of the two types of queries:
+ * - SELECT shard_name - shard_size (if useShardMinMaxQuery is false)
+ * - SELECT shard_id, shard_minvalue, shard_maxvalue, shard_size (if true)
+ */
+static char *
+GenerateShardStatisticsQueryForShardList(List *shardIntervalList, bool
+										 useShardMinMaxQuery)
+{
+	StringInfo selectQuery = makeStringInfo();
+
+	ShardInterval *shardInterval = NULL;
+	foreach_ptr(shardInterval, shardIntervalList)
+	{
+		uint64 shardId = shardInterval->shardId;
+		Oid schemaId = get_rel_namespace(shardInterval->relationId);
+		char *schemaName = get_namespace_name(schemaId);
+		char *shardName = get_rel_name(shardInterval->relationId);
+		AppendShardIdToName(&shardName, shardId);
+
+		char *shardQualifiedName = quote_qualified_identifier(schemaName, shardName);
+		char *quotedShardName = quote_literal_cstr(shardQualifiedName);
+
+		if (useShardMinMaxQuery)
+		{
+			AppendShardSizeMinMaxQuery(selectQuery, shardId, shardInterval, shardName,
+									   quotedShardName);
+		}
+		else
+		{
+			AppendShardSizeQuery(selectQuery, shardInterval, quotedShardName);
+		}
+		appendStringInfo(selectQuery, " UNION ALL ");
+	}
+
+	return selectQuery->data;
+}
+
+
+/*
+ * AppendShardSizeMinMaxQuery appends a query in the following form to selectQuery
+ * SELECT shard_id, shard_minvalue, shard_maxvalue, shard_size
+ */
+static void
+AppendShardSizeMinMaxQuery(StringInfo selectQuery, uint64 shardId,
+						   ShardInterval *shardInterval, char *shardName,
+						   char *quotedShardName)
+{
+	if (PartitionMethod(shardInterval->relationId) == DISTRIBUTE_BY_APPEND)
+	{
+		/* fill in the partition column name */
+		const uint32 unusedTableId = 1;
+		Var *partitionColumn = PartitionColumn(shardInterval->relationId,
+											   unusedTableId);
+		char *partitionColumnName = get_attname(shardInterval->relationId,
+												partitionColumn->varattno, false);
+		appendStringInfo(selectQuery,
+						 "SELECT " UINT64_FORMAT
+						 " AS shard_id, min(%s)::text AS shard_minvalue, max(%s)::text AS shard_maxvalue, pg_relation_size(%s) AS shard_size FROM %s ",
+						 shardId, partitionColumnName,
+						 partitionColumnName,
+						 quotedShardName, shardName);
+	}
+	else
+	{
+		/* we don't need to update min/max for non-append distributed tables because they don't change */
+		appendStringInfo(selectQuery,
+						 "SELECT " UINT64_FORMAT
+						 " AS shard_id, NULL::text AS shard_minvalue, NULL::text AS shard_maxvalue, pg_relation_size(%s) AS shard_size ",
+						 shardId, quotedShardName);
+	}
+}
+
+
+/*
+ * AppendShardSizeQuery appends a query in the following form to selectQuery
+ * SELECT shard_name, shard_size
+ */
+static void
+AppendShardSizeQuery(StringInfo selectQuery, ShardInterval *shardInterval,
+					 char *quotedShardName)
+{
+	appendStringInfo(selectQuery, "SELECT %s AS shard_name, ", quotedShardName);
+	appendStringInfo(selectQuery, PG_RELATION_SIZE_FUNCTION, quotedShardName);
+}
+
+
 /*
  * ErrorIfNotSuitableToGetSize determines whether the table is suitable to find
  * its' size with internal functions.

src/backend/distributed/metadata/node_metadata.c

@@ -443,7 +443,7 @@ SetUpDistributedTableDependencies(WorkerNode *newWorkerNode)
 		{
 			MarkNodeHasMetadata(newWorkerNode->workerName, newWorkerNode->workerPort,
 								true);
-			TriggerMetadataSync(MyDatabaseId);
+			TriggerMetadataSyncOnCommit();
 		}
 	}
 }
@@ -809,7 +809,7 @@ master_update_node(PG_FUNCTION_ARGS)
 	 */
 	if (UnsetMetadataSyncedForAll())
 	{
-		TriggerMetadataSync(MyDatabaseId);
+		TriggerMetadataSyncOnCommit();
 	}
 
 	if (handle != NULL)

src/backend/distributed/operations/stage_protocol.c

@@ -32,7 +32,9 @@
 #include "distributed/connection_management.h"
 #include "distributed/deparse_shard_query.h"
 #include "distributed/distributed_planner.h"
+#include "distributed/foreign_key_relationship.h"
 #include "distributed/listutils.h"
+#include "distributed/lock_graph.h"
 #include "distributed/multi_client_executor.h"
 #include "distributed/multi_executor.h"
 #include "distributed/metadata_utility.h"
@@ -65,11 +67,21 @@ static List * RelationShardListForShardCreate(ShardInterval *shardInterval);
 static bool WorkerShardStats(ShardPlacement *placement, Oid relationId,
 							 const char *shardName, uint64 *shardSize,
 							 text **shardMinValue, text **shardMaxValue);
+static void UpdateTableStatistics(Oid relationId);
+static void ReceiveAndUpdateShardsSizeAndMinMax(List *connectionList);
+static void UpdateShardSizeAndMinMax(uint64 shardId, ShardInterval *shardInterval, Oid
+									 relationId, List *shardPlacementList, uint64
+									 shardSize, text *shardMinValue,
+									 text *shardMaxValue);
+static bool ProcessShardStatisticsRow(PGresult *result, int64 rowIndex, uint64 *shardId,
+									  text **shardMinValue, text **shardMaxValue,
+									  uint64 *shardSize);
 
 /* exports for SQL callable functions */
 PG_FUNCTION_INFO_V1(master_create_empty_shard);
 PG_FUNCTION_INFO_V1(master_append_table_to_shard);
 PG_FUNCTION_INFO_V1(master_update_shard_statistics);
+PG_FUNCTION_INFO_V1(citus_update_table_statistics);
 
 
 /*
@@ -361,6 +373,23 @@ master_update_shard_statistics(PG_FUNCTION_ARGS)
 }
 
 
+/*
+ * citus_update_table_statistics updates metadata (shard size and shard min/max
+ * values) of the shards of the given table
+ */
+Datum
+citus_update_table_statistics(PG_FUNCTION_ARGS)
+{
+	Oid distributedTableId = PG_GETARG_OID(0);
+
+	CheckCitusVersion(ERROR);
+
+	UpdateTableStatistics(distributedTableId);
+
+	PG_RETURN_VOID();
+}
+
+
 /*
  * CheckDistributedTable checks if the given relationId corresponds to a
  * distributed table. If it does not, the function errors out.
@@ -776,7 +805,6 @@ UpdateShardStatistics(int64 shardId)
 {
 	ShardInterval *shardInterval = LoadShardInterval(shardId);
 	Oid relationId = shardInterval->relationId;
-	char storageType = shardInterval->storageType;
 	bool statsOK = false;
 	uint64 shardSize = 0;
 	text *minValue = NULL;
@@ -819,36 +847,176 @@ UpdateShardStatistics(int64 shardId)
 						  errdetail("Setting shard statistics to NULL")));
 	}
 
-	/* make sure we don't process cancel signals */
-	HOLD_INTERRUPTS();
+	UpdateShardSizeAndMinMax(shardId, shardInterval, relationId, shardPlacementList,
+							 shardSize, minValue, maxValue);
+	return shardSize;
+}
 
-	/* update metadata for each shard placement we appended to */
+
+/*
+ * UpdateTableStatistics updates metadata (shard size and shard min/max values)
+ * of the shards of the given table. Follows a similar logic to citus_shard_sizes function.
+ */
+static void
+UpdateTableStatistics(Oid relationId)
+{
+	List *citusTableIds = NIL;
+	citusTableIds = lappend_oid(citusTableIds, relationId);
+
+	/* we want to use a distributed transaction here to detect distributed deadlocks */
+	bool useDistributedTransaction = true;
+
+	/* we also want shard min/max values for append distributed tables */
+	bool useShardMinMaxQuery = true;
+
+	List *connectionList = SendShardStatisticsQueriesInParallel(citusTableIds,
+																useDistributedTransaction,
+																useShardMinMaxQuery);
+
+	ReceiveAndUpdateShardsSizeAndMinMax(connectionList);
+}
+
+
+/*
+ * ReceiveAndUpdateShardsSizeAndMinMax receives shard id, size
+ * and min max results from the given connection list, and updates
+ * respective entries in pg_dist_placement and pg_dist_shard
+ */
+static void
+ReceiveAndUpdateShardsSizeAndMinMax(List *connectionList)
+{
+	/*
+	 * From the connection list, we will not get all the shards, but
+	 * all the placements. We use a hash table to remember already visited shard ids
+	 * since we update all the different placements of a shard id at once.
+	 */
+	HTAB *alreadyVisitedShardPlacements = CreateOidVisitedHashSet();
+
+	MultiConnection *connection = NULL;
+	foreach_ptr(connection, connectionList)
+	{
+		if (PQstatus(connection->pgConn) != CONNECTION_OK)
+		{
+			continue;
+		}
+
+		bool raiseInterrupts = true;
+		PGresult *result = GetRemoteCommandResult(connection, raiseInterrupts);
+		if (!IsResponseOK(result))
+		{
+			ReportResultError(connection, result, WARNING);
+			continue;
+		}
+
+		int64 rowCount = PQntuples(result);
+		int64 colCount = PQnfields(result);
+
+		/* Although it is not expected */
+		if (colCount != UPDATE_SHARD_STATISTICS_COLUMN_COUNT)
+		{
+			ereport(WARNING, (errmsg("unexpected number of columns from "
+									 "master_update_table_statistics")));
+			continue;
+		}
+
+		for (int64 rowIndex = 0; rowIndex < rowCount; rowIndex++)
+		{
+			uint64 shardId = 0;
+			text *shardMinValue = NULL;
+			text *shardMaxValue = NULL;
+			uint64 shardSize = 0;
+
+			if (!ProcessShardStatisticsRow(result, rowIndex, &shardId, &shardMinValue,
+										   &shardMaxValue, &shardSize))
+			{
+				/* this row has no valid shard statistics */
+				continue;
+			}
+
+			if (OidVisited(alreadyVisitedShardPlacements, shardId))
+			{
+				/* We have already updated this placement list */
+				continue;
+			}
+
+			VisitOid(alreadyVisitedShardPlacements, shardId);
+
+			ShardInterval *shardInterval = LoadShardInterval(shardId);
+			Oid relationId = shardInterval->relationId;
+			List *shardPlacementList = ActiveShardPlacementList(shardId);
+
+			UpdateShardSizeAndMinMax(shardId, shardInterval, relationId,
+									 shardPlacementList, shardSize, shardMinValue,
+									 shardMaxValue);
+		}
+		PQclear(result);
+		ForgetResults(connection);
+	}
+	hash_destroy(alreadyVisitedShardPlacements);
+}
+
+
+/*
+ * ProcessShardStatisticsRow processes a row of shard statistics of the input PGresult
+ * - it returns true if this row belongs to a valid shard
+ * - it returns false if this row has no valid shard statistics (shardId = INVALID_SHARD_ID)
+ */
+static bool
+ProcessShardStatisticsRow(PGresult *result, int64 rowIndex, uint64 *shardId,
+						  text **shardMinValue, text **shardMaxValue, uint64 *shardSize)
+{
+	*shardId = ParseIntField(result, rowIndex, 0);
+
+	/* check for the dummy entries we put so that UNION ALL wouldn't complain */
+	if (*shardId == INVALID_SHARD_ID)
+	{
+		/* this row has no valid shard statistics */
+		return false;
+	}
+
+	char *minValueResult = PQgetvalue(result, rowIndex, 1);
+	char *maxValueResult = PQgetvalue(result, rowIndex, 2);
+	*shardMinValue = cstring_to_text(minValueResult);
+	*shardMaxValue = cstring_to_text(maxValueResult);
+	*shardSize = ParseIntField(result, rowIndex, 3);
+	return true;
+}
+
+
+/*
+ * UpdateShardSizeAndMinMax updates the shardlength (shard size) of the given
+ * shard and its placements in pg_dist_placement, and updates the shard min value
+ * and shard max value of the given shard in pg_dist_shard if the relationId belongs
+ * to an append-distributed table
+ */
+static void
+UpdateShardSizeAndMinMax(uint64 shardId, ShardInterval *shardInterval, Oid relationId,
+						 List *shardPlacementList, uint64 shardSize, text *shardMinValue,
+						 text *shardMaxValue)
+{
+	char storageType = shardInterval->storageType;
+
+	ShardPlacement *placement = NULL;
+
+	/* update metadata for each shard placement */
 	foreach_ptr(placement, shardPlacementList)
 	{
 		uint64 placementId = placement->placementId;
 		int32 groupId = placement->groupId;
 
 		DeleteShardPlacementRow(placementId);
-		InsertShardPlacementRow(shardId, placementId, SHARD_STATE_ACTIVE, shardSize,
+		InsertShardPlacementRow(shardId, placementId, SHARD_STATE_ACTIVE,
+								shardSize,
 								groupId);
 	}
 
 	/* only update shard min/max values for append-partitioned tables */
-	if (IsCitusTableType(relationId, APPEND_DISTRIBUTED))
+	if (PartitionMethod(relationId) == DISTRIBUTE_BY_APPEND)
 	{
 		DeleteShardRow(shardId);
-		InsertShardRow(relationId, shardId, storageType, minValue, maxValue);
+		InsertShardRow(relationId, shardId, storageType, shardMinValue,
+					   shardMaxValue);
 	}
-
-	if (QueryCancelPending)
-	{
-		ereport(WARNING, (errmsg("cancel requests are ignored during metadata update")));
-		QueryCancelPending = false;
-	}
-
-	RESUME_INTERRUPTS();
-
-	return shardSize;
 }
 
 

src/backend/distributed/operations/worker_node_manager.c

@@ -318,20 +318,6 @@ ActivePrimaryNodeCount(void)
 }
 
 
-/*
- * ActiveReadableNonCoordinatorNodeCount returns the number of groups with a node we can read from.
- * This method excludes coordinator even if it is added as a worker.
- */
-uint32
-ActiveReadableNonCoordinatorNodeCount(void)
-{
-	List *workerNodeList = ActiveReadableNonCoordinatorNodeList();
-	uint32 liveWorkerCount = list_length(workerNodeList);
-
-	return liveWorkerCount;
-}
-
-
 /*
  * NodeIsCoordinator returns true if the given node represents the coordinator.
  */

src/backend/distributed/planner/deparse_shard_query.c

@@ -13,6 +13,8 @@
 #include "c.h"
 
 #include "access/heapam.h"
+#include "access/htup_details.h"
+#include "catalog/pg_constraint.h"
 #include "distributed/citus_nodefuncs.h"
 #include "distributed/citus_ruleutils.h"
 #include "distributed/deparse_shard_query.h"
@@ -34,10 +36,11 @@
 #include "storage/lock.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
+#include "utils/syscache.h"
 
 
-static void UpdateTaskQueryString(Query *query, Oid distributedTableId,
-								  RangeTblEntry *valuesRTE, Task *task);
+static void UpdateTaskQueryString(Query *query, Task *task);
+static RelationShard * FindRelationShard(Oid inputRelationId, List *relationShardList);
 static void ConvertRteToSubqueryWithEmptyResult(RangeTblEntry *rte);
 static bool ShouldLazyDeparseQuery(Task *task);
 static char * DeparseTaskQuery(Task *task, Query *query);
@@ -52,27 +55,43 @@ RebuildQueryStrings(Job *workerJob)
 {
 	Query *originalQuery = workerJob->jobQuery;
 	List *taskList = workerJob->taskList;
-	Oid relationId = ((RangeTblEntry *) linitial(originalQuery->rtable))->relid;
-	RangeTblEntry *valuesRTE = ExtractDistributedInsertValuesRTE(originalQuery);
-
 	Task *task = NULL;
 
+	if (originalQuery->commandType == CMD_INSERT)
+	{
+		AddInsertAliasIfNeeded(originalQuery);
+	}
+
 	foreach_ptr(task, taskList)
 	{
 		Query *query = originalQuery;
 
-		if (UpdateOrDeleteQuery(query) && list_length(taskList) > 1)
+		/*
+		 * Copy the query if there are multiple tasks. If there is a single
+		 * task, we scribble on the original query to avoid the copying
+		 * overhead.
+		 */
+		if (list_length(taskList) > 1)
 		{
 			query = copyObject(originalQuery);
 		}
+
+		if (UpdateOrDeleteQuery(query))
+		{
+			/*
+			 * For UPDATE and DELETE queries, we may have subqueries and joins, so
+			 * we use relation shard list to update shard names and call
+			 * pg_get_query_def() directly.
+			 */
+			List *relationShardList = task->relationShardList;
+			UpdateRelationToShardNames((Node *) query, relationShardList);
+		}
 		else if (query->commandType == CMD_INSERT && task->modifyWithSubquery)
 		{
 			/* for INSERT..SELECT, adjust shard names in SELECT part */
 			List *relationShardList = task->relationShardList;
 			ShardInterval *shardInterval = LoadShardInterval(task->anchorShardId);
 
-			query = copyObject(originalQuery);
-
 			RangeTblEntry *copiedInsertRte = ExtractResultRelationRTEOrError(query);
 			RangeTblEntry *copiedSubqueryRte = ExtractSelectRangeTableEntry(query);
 			Query *copiedSubquery = copiedSubqueryRte->subquery;
@@ -85,29 +104,18 @@ RebuildQueryStrings(Job *workerJob)
 
 			ReorderInsertSelectTargetLists(query, copiedInsertRte, copiedSubqueryRte);
 
-			/* setting an alias simplifies deparsing of RETURNING */
-			if (copiedInsertRte->alias == NULL)
-			{
-				Alias *alias = makeAlias(CITUS_TABLE_ALIAS, NIL);
-				copiedInsertRte->alias = alias;
-			}
-
 			UpdateRelationToShardNames((Node *) copiedSubquery, relationShardList);
 		}
-		else if (query->commandType == CMD_INSERT && (query->onConflict != NULL ||
-													  valuesRTE != NULL))
+
+		if (query->commandType == CMD_INSERT)
 		{
+			RangeTblEntry *modifiedRelationRTE = linitial(originalQuery->rtable);
+
 			/*
-			 * Always an alias in UPSERTs and multi-row INSERTs to avoid
-			 * deparsing issues (e.g. RETURNING might reference the original
-			 * table name, which has been replaced by a shard name).
+			 * We store the modified relaiton ID in the task so we can lazily call
+			 * deparse_shard_query when the string is needed
 			 */
-			RangeTblEntry *rangeTableEntry = linitial(query->rtable);
-			if (rangeTableEntry->alias == NULL)
-			{
-				Alias *alias = makeAlias(CITUS_TABLE_ALIAS, NIL);
-				rangeTableEntry->alias = alias;
-			}
+			task->anchorDistributedTableId = modifiedRelationRTE->relid;
 		}
 
 		bool isQueryObjectOrText = GetTaskQueryType(task) == TASK_QUERY_TEXT ||
@@ -117,7 +125,7 @@ RebuildQueryStrings(Job *workerJob)
 								? "(null)"
 								: ApplyLogRedaction(TaskQueryString(task)))));
 
-		UpdateTaskQueryString(query, relationId, valuesRTE, task);
+		UpdateTaskQueryString(query, task);
 
 		/*
 		 * If parameters were resolved in the job query, then they are now also
@@ -131,54 +139,69 @@ RebuildQueryStrings(Job *workerJob)
 }
 
 
+/*
+ * AddInsertAliasIfNeeded adds an alias in UPSERTs and multi-row INSERTs to avoid
+ * deparsing issues (e.g. RETURNING might reference the original table name,
+ * which has been replaced by a shard name).
+ */
+void
+AddInsertAliasIfNeeded(Query *query)
+{
+	Assert(query->commandType == CMD_INSERT);
+
+	if (query->onConflict == NULL &&
+		ExtractDistributedInsertValuesRTE(query) == NULL)
+	{
+		/* simple single-row insert does not need an alias */
+		return;
+	}
+
+	RangeTblEntry *rangeTableEntry = linitial(query->rtable);
+	if (rangeTableEntry->alias != NULL)
+	{
+		/* INSERT already has an alias */
+		return;
+	}
+
+	Alias *alias = makeAlias(CITUS_TABLE_ALIAS, NIL);
+	rangeTableEntry->alias = alias;
+}
+
+
 /*
  * UpdateTaskQueryString updates the query string stored within the provided
  * Task. If the Task has row values from a multi-row INSERT, those are injected
- * into the provided query (using the provided valuesRTE, which must belong to
- * the query) before deparse occurs (the query's full VALUES list will be
- * restored before this function returns).
+ * into the provided query before deparse occurs (the query's full VALUES list
+ * will be restored before this function returns).
  */
 static void
-UpdateTaskQueryString(Query *query, Oid distributedTableId, RangeTblEntry *valuesRTE,
-					  Task *task)
+UpdateTaskQueryString(Query *query, Task *task)
 {
 	List *oldValuesLists = NIL;
-
-	if (valuesRTE != NULL)
-	{
-		Assert(valuesRTE->rtekind == RTE_VALUES);
-		Assert(task->rowValuesLists != NULL);
-
-		oldValuesLists = valuesRTE->values_lists;
-		valuesRTE->values_lists = task->rowValuesLists;
-	}
-
-	if (query->commandType != CMD_INSERT)
-	{
-		/*
-		 * For UPDATE and DELETE queries, we may have subqueries and joins, so
-		 * we use relation shard list to update shard names and call
-		 * pg_get_query_def() directly.
-		 */
-		List *relationShardList = task->relationShardList;
-		UpdateRelationToShardNames((Node *) query, relationShardList);
-	}
-	else if (ShouldLazyDeparseQuery(task))
-	{
-		/*
-		 * not all insert queries are copied before calling this
-		 * function, so we do it here
-		 */
-		query = copyObject(query);
-	}
+	RangeTblEntry *valuesRTE = NULL;
 
 	if (query->commandType == CMD_INSERT)
 	{
-		/*
-		 * We store this in the task so we can lazily call
-		 * deparse_shard_query when the string is needed
-		 */
-		task->anchorDistributedTableId = distributedTableId;
+		/* extract the VALUES from the INSERT */
+		valuesRTE = ExtractDistributedInsertValuesRTE(query);
+
+		if (valuesRTE != NULL)
+		{
+			Assert(valuesRTE->rtekind == RTE_VALUES);
+			Assert(task->rowValuesLists != NULL);
+
+			oldValuesLists = valuesRTE->values_lists;
+			valuesRTE->values_lists = task->rowValuesLists;
+		}
+
+		if (ShouldLazyDeparseQuery(task))
+		{
+			/*
+			 * not all insert queries are copied before calling this
+			 * function, so we do it here
+			 */
+			query = copyObject(query);
+		}
 	}
 
 	SetTaskQueryIfShouldLazyDeparse(task, query);
@@ -203,9 +226,6 @@ bool
 UpdateRelationToShardNames(Node *node, List *relationShardList)
 {
 	uint64 shardId = INVALID_SHARD_ID;
-	Oid relationId = InvalidOid;
-	ListCell *relationShardCell = NULL;
-	RelationShard *relationShard = NULL;
 
 	if (node == NULL)
 	{
@@ -238,24 +258,8 @@ UpdateRelationToShardNames(Node *node, List *relationShardList)
 		return false;
 	}
 
-	/*
-	 * Search for the restrictions associated with the RTE. There better be
-	 * some, otherwise this query wouldn't be eligible as a router query.
-	 *
-	 * FIXME: We should probably use a hashtable here, to do efficient
-	 * lookup.
-	 */
-	foreach(relationShardCell, relationShardList)
-	{
-		relationShard = (RelationShard *) lfirst(relationShardCell);
-
-		if (newRte->relid == relationShard->relationId)
-		{
-			break;
-		}
-
-		relationShard = NULL;
-	}
+	RelationShard *relationShard = FindRelationShard(newRte->relid,
+													 relationShardList);
 
 	bool replaceRteWithNullValues = relationShard == NULL ||
 									relationShard->shardId == INVALID_SHARD_ID;
@@ -266,7 +270,7 @@ UpdateRelationToShardNames(Node *node, List *relationShardList)
 	}
 
 	shardId = relationShard->shardId;
-	relationId = relationShard->relationId;
+	Oid relationId = relationShard->relationId;
 
 	char *relationName = get_rel_name(relationId);
 	AppendShardIdToName(&relationName, shardId);
@@ -281,72 +285,28 @@ UpdateRelationToShardNames(Node *node, List *relationShardList)
 
 
 /*
- * UpdateRelationsToLocalShardTables walks over the query tree and appends shard ids to
- * relations. The caller is responsible for ensuring that the resulting Query can
- * be executed locally.
+ * FindRelationShard finds the RelationShard for shard relation with
+ * given Oid if exists in given relationShardList. Otherwise, returns NULL.
  */
-bool
-UpdateRelationsToLocalShardTables(Node *node, List *relationShardList)
+static RelationShard *
+FindRelationShard(Oid inputRelationId, List *relationShardList)
 {
-	if (node == NULL)
-	{
-		return false;
-	}
-
-	/* want to look at all RTEs, even in subqueries, CTEs and such */
-	if (IsA(node, Query))
-	{
-		return query_tree_walker((Query *) node, UpdateRelationsToLocalShardTables,
-								 relationShardList, QTW_EXAMINE_RTES_BEFORE);
-	}
-
-	if (!IsA(node, RangeTblEntry))
-	{
-		return expression_tree_walker(node, UpdateRelationsToLocalShardTables,
-									  relationShardList);
-	}
-
-	RangeTblEntry *newRte = (RangeTblEntry *) node;
-
-	if (newRte->rtekind != RTE_RELATION)
-	{
-		return false;
-	}
+	RelationShard *relationShard = NULL;
 
 	/*
 	 * Search for the restrictions associated with the RTE. There better be
 	 * some, otherwise this query wouldn't be eligible as a router query.
-	 *
-	 * FIXME: We should probably use a hashtable here, to do efficient
-	 * lookup.
+	 * FIXME: We should probably use a hashtable here, to do efficient lookup.
 	 */
-	ListCell *relationShardCell = NULL;
-	RelationShard *relationShard = NULL;
-
-	foreach(relationShardCell, relationShardList)
+	foreach_ptr(relationShard, relationShardList)
 	{
-		relationShard = (RelationShard *) lfirst(relationShardCell);
-
-		if (newRte->relid == relationShard->relationId)
+		if (inputRelationId == relationShard->relationId)
 		{
-			break;
+			return relationShard;
 		}
-
-		relationShard = NULL;
 	}
 
-	/* the function should only be called with local shards */
-	if (relationShard == NULL)
-	{
-		return true;
-	}
-
-	Oid shardOid = GetTableLocalShardOid(relationShard->relationId,
-										 relationShard->shardId);
-
-	newRte->relid = shardOid;
-
-	return false;
+	return NULL;
 }
 
 

src/backend/distributed/planner/intermediate_result_pruning.c

@@ -32,7 +32,7 @@ bool LogIntermediateResults = false;
 static List * FindSubPlansUsedInNode(Node *node, SubPlanAccessType accessType);
 static void AppendAllAccessedWorkerNodes(IntermediateResultsHashEntry *entry,
 										 DistributedPlan *distributedPlan,
-										 int workerNodeCount);
+										 int nodeCount);
 static void AppendAllWorkerNodes(IntermediateResultsHashEntry *entry);
 static List * FindAllRemoteWorkerNodesUsingSubplan(IntermediateResultsHashEntry *entry);
 static List * RemoveLocalNodeFromWorkerList(List *workerNodeList);
@@ -154,7 +154,7 @@ RecordSubplanExecutionsOnNodes(HTAB *intermediateResultsHash,
 	List *usedSubPlanNodeList = distributedPlan->usedSubPlanNodeList;
 	List *subPlanList = distributedPlan->subPlanList;
 	ListCell *subPlanCell = NULL;
-	int workerNodeCount = ActiveReadableNonCoordinatorNodeCount();
+	int nodeCount = list_length(ActiveReadableNodeList());
 
 	foreach(subPlanCell, usedSubPlanNodeList)
 	{
@@ -170,7 +170,7 @@ RecordSubplanExecutionsOnNodes(HTAB *intermediateResultsHash,
 		 * will be written to a local file and sent to all nodes. Note that the
 		 * remaining subplans in the distributed plan should still be traversed.
 		 */
-		if (list_length(entry->nodeIdList) == workerNodeCount && entry->writeLocalFile)
+		if (list_length(entry->nodeIdList) == nodeCount && entry->writeLocalFile)
 		{
 			elog(DEBUG4, "Subplan %s is used in all workers", resultId);
 			continue;
@@ -190,7 +190,7 @@ RecordSubplanExecutionsOnNodes(HTAB *intermediateResultsHash,
 			 * workers will be in the node list. We can improve intermediate result
 			 * pruning by deciding which reference table shard will be accessed earlier.
 			 */
-			AppendAllAccessedWorkerNodes(entry, distributedPlan, workerNodeCount);
+			AppendAllAccessedWorkerNodes(entry, distributedPlan, nodeCount);
 
 			elog(DEBUG4, "Subplan %s is used in %lu", resultId, distributedPlan->planId);
 		}
@@ -231,7 +231,7 @@ RecordSubplanExecutionsOnNodes(HTAB *intermediateResultsHash,
 static void
 AppendAllAccessedWorkerNodes(IntermediateResultsHashEntry *entry,
 							 DistributedPlan *distributedPlan,
-							 int workerNodeCount)
+							 int nodeCount)
 {
 	List *taskList = distributedPlan->workerJob->taskList;
 	ListCell *taskCell = NULL;
@@ -254,7 +254,7 @@ AppendAllAccessedWorkerNodes(IntermediateResultsHashEntry *entry,
 				list_append_unique_int(entry->nodeIdList, placement->nodeId);
 
 			/* early return if all the workers are accessed */
-			if (list_length(entry->nodeIdList) == workerNodeCount &&
+			if (list_length(entry->nodeIdList) == nodeCount &&
 				entry->writeLocalFile)
 			{
 				return;
@@ -272,7 +272,7 @@ AppendAllAccessedWorkerNodes(IntermediateResultsHashEntry *entry,
 static void
 AppendAllWorkerNodes(IntermediateResultsHashEntry *entry)
 {
-	List *workerNodeList = ActiveReadableNonCoordinatorNodeList();
+	List *workerNodeList = ActiveReadableNodeList();
 
 	WorkerNode *workerNode = NULL;
 	foreach_ptr(workerNode, workerNodeList)
@@ -383,10 +383,11 @@ RemoveLocalNodeFromWorkerList(List *workerNodeList)
 		{
 			return list_delete_cell_compat(workerNodeList, workerNodeCell, prev);
 		}
+		#if PG_VERSION_NUM < PG_VERSION_13
+		prev = workerNodeCell;
+		#endif
 	}
-	#if PG_VERSION_NUM < PG_VERSION_13
-	prev = workerNodeCell;
-	#endif
+
 	return workerNodeList;
 }
 

src/backend/distributed/planner/local_plan_cache.c

@@ -16,7 +16,9 @@
 #include "distributed/local_plan_cache.h"
 #include "distributed/deparse_shard_query.h"
 #include "distributed/citus_ruleutils.h"
+#include "distributed/insert_select_planner.h"
 #include "distributed/metadata_cache.h"
+#include "distributed/multi_executor.h"
 #include "distributed/version_compat.h"
 #if PG_VERSION_NUM >= PG_VERSION_12
 #include "optimizer/optimizer.h"
@@ -26,13 +28,21 @@
 #include "optimizer/clauses.h"
 
 
+static Query * GetLocalShardQueryForCache(Query *jobQuery, Task *task,
+										  ParamListInfo paramListInfo);
+static char * DeparseLocalShardQuery(Query *jobQuery, List *relationShardList,
+									 Oid anchorDistributedTableId, int64 anchorShardId);
+static int ExtractParameterTypesForParamListInfo(ParamListInfo originalParamListInfo,
+												 Oid **parameterTypes);
+
 /*
  * CacheLocalPlanForShardQuery replaces the relation OIDs in the job query
  * with shard relation OIDs and then plans the query and caches the result
  * in the originalDistributedPlan (which may be preserved across executions).
  */
 void
-CacheLocalPlanForShardQuery(Task *task, DistributedPlan *originalDistributedPlan)
+CacheLocalPlanForShardQuery(Task *task, DistributedPlan *originalDistributedPlan,
+							ParamListInfo paramListInfo)
 {
 	PlannedStmt *localPlan = GetCachedLocalPlan(task, originalDistributedPlan);
 	if (localPlan != NULL)
@@ -58,14 +68,14 @@ CacheLocalPlanForShardQuery(Task *task, DistributedPlan *originalDistributedPlan
 	 * We prefer to use jobQuery (over task->query) because we don't want any
 	 * functions/params to have been evaluated in the cached plan.
 	 */
-	Query *shardQuery = copyObject(originalDistributedPlan->workerJob->jobQuery);
+	Query *jobQuery = copyObject(originalDistributedPlan->workerJob->jobQuery);
 
-	UpdateRelationsToLocalShardTables((Node *) shardQuery, task->relationShardList);
+	Query *localShardQuery = GetLocalShardQueryForCache(jobQuery, task, paramListInfo);
 
-	LOCKMODE lockMode = GetQueryLockMode(shardQuery);
+	LOCKMODE lockMode = GetQueryLockMode(localShardQuery);
 
 	/* fast path queries can only have a single RTE by definition */
-	RangeTblEntry *rangeTableEntry = (RangeTblEntry *) linitial(shardQuery->rtable);
+	RangeTblEntry *rangeTableEntry = (RangeTblEntry *) linitial(localShardQuery->rtable);
 
 	/*
 	 * If the shard has been created in this transction, we wouldn't see the relationId
@@ -73,24 +83,16 @@ CacheLocalPlanForShardQuery(Task *task, DistributedPlan *originalDistributedPlan
 	 */
 	if (rangeTableEntry->relid == InvalidOid)
 	{
-		pfree(shardQuery);
+		pfree(jobQuery);
+		pfree(localShardQuery);
 		MemoryContextSwitchTo(oldContext);
 		return;
 	}
 
-	if (IsLoggableLevel(DEBUG5))
-	{
-		StringInfo queryString = makeStringInfo();
-		pg_get_query_def(shardQuery, queryString);
-
-		ereport(DEBUG5, (errmsg("caching plan for query: %s",
-								queryString->data)));
-	}
-
 	LockRelationOid(rangeTableEntry->relid, lockMode);
 
 	LocalPlannedStatement *localPlannedStatement = CitusMakeNode(LocalPlannedStatement);
-	localPlan = planner_compat(shardQuery, 0, NULL);
+	localPlan = planner_compat(localShardQuery, 0, NULL);
 	localPlannedStatement->localPlan = localPlan;
 	localPlannedStatement->shardId = task->anchorShardId;
 	localPlannedStatement->localGroupId = GetLocalGroupId();
@@ -103,6 +105,130 @@ CacheLocalPlanForShardQuery(Task *task, DistributedPlan *originalDistributedPlan
 }
 
 
+/*
+ * GetLocalShardQueryForCache is a helper function which generates
+ * the local shard query based on the jobQuery. The function should
+ * not be used for generic purposes, it is specialized for local cached
+ * queries.
+ *
+ * It is not guaranteed to have consistent attribute numbers on the shards
+ * and on the shell (e.g., distributed/reference tables) due to DROP COLUMN
+ * commands.
+ *
+ * To avoid any edge cases due to such discrepancies, we first deparse the
+ * jobQuery with the tables replaced to shards, and parse the query string
+ * back. This is normally a very expensive operation, however we only do it
+ * once per cached local plan, which is acceptable.
+ */
+static Query *
+GetLocalShardQueryForCache(Query *jobQuery, Task *task, ParamListInfo orig_paramListInfo)
+{
+	char *shardQueryString =
+		DeparseLocalShardQuery(jobQuery, task->relationShardList,
+							   task->anchorDistributedTableId,
+							   task->anchorShardId);
+	ereport(DEBUG5, (errmsg("Local shard query that is going to be cached: %s",
+							shardQueryString)));
+
+	Oid *parameterTypes = NULL;
+	int numberOfParameters =
+		ExtractParameterTypesForParamListInfo(orig_paramListInfo, &parameterTypes);
+
+	Query *localShardQuery =
+		ParseQueryString(shardQueryString, parameterTypes, numberOfParameters);
+
+	return localShardQuery;
+}
+
+
+/*
+ * DeparseLocalShardQuery is a helper function to deparse given jobQuery for the shard(s)
+ * identified by the relationShardList, anchorDistributedTableId and anchorShardId.
+ *
+ * For the details and comparison with TaskQueryString(), see the comments in the function.
+ */
+static char *
+DeparseLocalShardQuery(Query *jobQuery, List *relationShardList, Oid
+					   anchorDistributedTableId, int64 anchorShardId)
+{
+	StringInfo queryString = makeStringInfo();
+
+	/*
+	 * We imitate what TaskQueryString() does, but we cannot rely on that function
+	 * as the parameters might have been already resolved on the QueryTree in the
+	 * task. Instead, we operate on the jobQuery where are sure that the
+	 * coordination evaluation has not happened.
+	 *
+	 * Local shard queries are only applicable for local cached query execution.
+	 * In the local cached query execution mode, we can use a query structure
+	 * (or query string) with unevaluated expressions as we allow function calls
+	 * to be evaluated when the query on the shard is executed (e.g., do no have
+	 * coordinator evaluation, instead let Postgres executor evaluate values).
+	 *
+	 * Additionally, we can allow them to be evaluated again because they are stable,
+	 * and we do not cache plans / use unevaluated query strings for queries containing
+	 * volatile functions.
+	 */
+	if (jobQuery->commandType == CMD_INSERT)
+	{
+		/*
+		 * We currently do not support INSERT .. SELECT here. To support INSERT..SELECT
+		 * queries, we should update the relation names to shard names in the SELECT
+		 * clause (e.g., UpdateRelationToShardNames()).
+		 */
+		Assert(!CheckInsertSelectQuery(jobQuery));
+
+		AddInsertAliasIfNeeded(jobQuery);
+
+		/*
+		 * For INSERT queries we cannot use pg_get_query_def. Mainly because we
+		 * cannot run UpdateRelationToShardNames on an INSERT query. This is
+		 * because the PG deparsing logic fails when trying to insert into a
+		 * RTE_FUNCTION (which is what will happen if you call
+		 * UpdateRelationToShardNames).
+		 */
+		deparse_shard_query(jobQuery, anchorDistributedTableId, anchorShardId,
+							queryString);
+	}
+	else
+	{
+		UpdateRelationToShardNames((Node *) jobQuery, relationShardList);
+
+		pg_get_query_def(jobQuery, queryString);
+	}
+
+	return queryString->data;
+}
+
+
+/*
+ * ExtractParameterTypesForParamListInfo is a helper function which helps to
+ * extract the parameter types of the given ParamListInfo via the second
+ * parameter of the function.
+ *
+ * The function also returns the number of parameters. If no parameter exists,
+ * the function returns 0.
+ */
+static int
+ExtractParameterTypesForParamListInfo(ParamListInfo originalParamListInfo,
+									  Oid **parameterTypes)
+{
+	*parameterTypes = NULL;
+
+	int numberOfParameters = 0;
+	if (originalParamListInfo != NULL)
+	{
+		const char **parameterValues = NULL;
+		ParamListInfo paramListInfo = copyParamList(originalParamListInfo);
+		ExtractParametersForLocalExecution(paramListInfo, parameterTypes,
+										   &parameterValues);
+		numberOfParameters = paramListInfo->numParams;
+	}
+
+	return numberOfParameters;
+}
+
+
 /*
  * GetCachedLocalPlan is a helper function which return the cached
  * plan in the distributedPlan for the given task if exists.

src/backend/distributed/planner/multi_explain.c

@@ -1063,7 +1063,7 @@ worker_save_query_explain_analyze(PG_FUNCTION_ARGS)
 
 	INSTR_TIME_SET_CURRENT(planStart);
 
-	PlannedStmt *plan = pg_plan_query_compat(query, NULL, 0, NULL);
+	PlannedStmt *plan = pg_plan_query_compat(query, NULL, CURSOR_OPT_PARALLEL_OK, NULL);
 
 	INSTR_TIME_SET_CURRENT(planDuration);
 	INSTR_TIME_SUBTRACT(planDuration, planStart);

src/backend/distributed/planner/multi_logical_optimizer.c

@@ -1614,7 +1614,19 @@ MasterAggregateExpression(Aggref *originalAggregate,
 		Expr *directarg;
 		foreach_ptr(directarg, originalAggregate->aggdirectargs)
 		{
-			if (!IsA(directarg, Const) && !IsA(directarg, Param))
+			/*
+			 * Need to replace nodes that contain any Vars with Vars referring
+			 * to the related column of the result set returned for the worker
+			 * aggregation.
+			 *
+			 * When there are no Vars, then the expression can be fully evaluated
+			 * on the coordinator, so we skip it here. This is not just an
+			 * optimization, but the result of the expression might require
+			 * calling the final function of the aggregate, and doing so when
+			 * there are no input rows (i.e.: with an empty tuple slot) is not
+			 * desirable for the node-executor methods.
+			 */
+			if (pull_var_clause_default((Node *) directarg) != NIL)
 			{
 				Var *var = makeVar(masterTableId, walkerContext->columnId,
 								   exprType((Node *) directarg),
@@ -3090,7 +3102,13 @@ WorkerAggregateExpressionList(Aggref *originalAggregate,
 		Expr *directarg;
 		foreach_ptr(directarg, originalAggregate->aggdirectargs)
 		{
-			if (!IsA(directarg, Const) && !IsA(directarg, Param))
+			/*
+			 * The worker aggregation should execute any node that contains any
+			 * Var nodes and return the result in the targetlist, so that the
+			 * combine query can then fetch the result via remote scan; see
+			 * MasterAggregateExpression.
+			 */
+			if (pull_var_clause_default((Node *) directarg) != NIL)
 			{
 				workerAggregateList = lappend(workerAggregateList, directarg);
 			}

src/backend/distributed/planner/shard_pruning.c

@@ -1576,6 +1576,22 @@ LowerShardBoundary(Datum partitionColumnValue, ShardInterval **shardIntervalCach
 	/* setup partitionColumnValue argument once */
 	fcSetArg(compareFunction, 0, partitionColumnValue);
 
+	/*
+	 * Now we test partitionColumnValue used in where clause such as
+	 * partCol > partitionColumnValue (or partCol >= partitionColumnValue)
+	 * against four possibilities, these are:
+	 * 1) partitionColumnValue falls into a specific shard, such that:
+	 *    partitionColumnValue >= shard[x].min, and
+	 *    partitionColumnValue < shard[x].max (or partitionColumnValue <= shard[x].max).
+	 * 2) partitionColumnValue < shard[x].min for all the shards
+	 * 3) partitionColumnValue > shard[x].max for all the shards
+	 * 4) partitionColumnValue falls in between two shards, such that:
+	 *    partitionColumnValue > shard[x].max and
+	 *    partitionColumnValue < shard[x+1].min
+	 *
+	 * For 1), we find that shard in below loop using binary search and
+	 * return the index of it. For the others, see the end of this function.
+	 */
 	while (lowerBoundIndex < upperBoundIndex)
 	{
 		int middleIndex = lowerBoundIndex + ((upperBoundIndex - lowerBoundIndex) / 2);
@@ -1608,7 +1624,7 @@ LowerShardBoundary(Datum partitionColumnValue, ShardInterval **shardIntervalCach
 			continue;
 		}
 
-		/* found interval containing partitionValue */
+		/* partitionColumnValue falls into a specific shard, possibility 1) */
 		return middleIndex;
 	}
 
@@ -1619,20 +1635,30 @@ LowerShardBoundary(Datum partitionColumnValue, ShardInterval **shardIntervalCach
 	 * (we'd have hit the return middleIndex; case otherwise). Figure out
 	 * whether there's possibly any interval containing a value that's bigger
 	 * than the partition key one.
+	 *
+	 * Also note that we initialized lowerBoundIndex with 0. Similarly,
+	 * we always set it to the index of the  shard that we consider as our
+	 * lower boundary during binary search.
 	 */
-	if (lowerBoundIndex == 0)
+	if (lowerBoundIndex == shardCount)
 	{
-		/* all intervals are bigger, thus return 0 */
-		return 0;
-	}
-	else if (lowerBoundIndex == shardCount)
-	{
-		/* partition value is bigger than all partition values */
+		/*
+		 * Since lowerBoundIndex is an inclusive index, being equal to shardCount
+		 * means all the shards have smaller values than partitionColumnValue,
+		 * which corresponds to possibility 3).
+		 * In that case, since we can't have a lower bound shard, we return
+		 * INVALID_SHARD_INDEX here.
+		 */
 		return INVALID_SHARD_INDEX;
 	}
 
-	/* value falls inbetween intervals */
-	return lowerBoundIndex + 1;
+	/*
+	 * partitionColumnValue is either smaller than all the shards or falls in
+	 * between two shards, which corresponds to possibility 2) or 4).
+	 * Knowing that lowerBoundIndex is an inclusive index, we directly return
+	 * it as the index for the lower bound shard here.
+	 */
+	return lowerBoundIndex;
 }
 
 
@@ -1652,6 +1678,23 @@ UpperShardBoundary(Datum partitionColumnValue, ShardInterval **shardIntervalCach
 	/* setup partitionColumnValue argument once */
 	fcSetArg(compareFunction, 0, partitionColumnValue);
 
+	/*
+	 * Now we test partitionColumnValue used in where clause such as
+	 * partCol < partitionColumnValue (or partCol <= partitionColumnValue)
+	 * against four possibilities, these are:
+	 * 1) partitionColumnValue falls into a specific shard, such that:
+	 *    partitionColumnValue <= shard[x].max, and
+	 *    partitionColumnValue > shard[x].min (or partitionColumnValue >= shard[x].min).
+	 * 2) partitionColumnValue > shard[x].max for all the shards
+	 * 3) partitionColumnValue < shard[x].min for all the shards
+	 * 4) partitionColumnValue falls in between two shards, such that:
+	 *    partitionColumnValue > shard[x].max and
+	 *    partitionColumnValue < shard[x+1].min
+	 *
+	 * For 1), we find that shard in below loop using binary search and
+	 * return the index of it. For the others, see the end of this function.
+	 */
+
 	while (lowerBoundIndex < upperBoundIndex)
 	{
 		int middleIndex = lowerBoundIndex + ((upperBoundIndex - lowerBoundIndex) / 2);
@@ -1684,7 +1727,7 @@ UpperShardBoundary(Datum partitionColumnValue, ShardInterval **shardIntervalCach
 			continue;
 		}
 
-		/* found interval containing partitionValue */
+		/* partitionColumnValue falls into a specific shard, possibility 1) */
 		return middleIndex;
 	}
 
@@ -1695,19 +1738,29 @@ UpperShardBoundary(Datum partitionColumnValue, ShardInterval **shardIntervalCach
 	 * (we'd have hit the return middleIndex; case otherwise). Figure out
 	 * whether there's possibly any interval containing a value that's smaller
 	 * than the partition key one.
+	 *
+	 * Also note that we initialized upperBoundIndex with shardCount. Similarly,
+	 * we always set it to the index of the next shard that we consider as our
+	 * upper boundary during binary search.
 	 */
-	if (upperBoundIndex == shardCount)
+	if (upperBoundIndex == 0)
 	{
-		/* all intervals are smaller, thus return 0 */
-		return shardCount - 1;
-	}
-	else if (upperBoundIndex == 0)
-	{
-		/* partition value is smaller than all partition values */
+		/*
+		 * Since upperBoundIndex is an exclusive index, being equal to 0 means
+		 * all the shards have greater values than partitionColumnValue, which
+		 * corresponds to possibility 3).
+		 * In that case, since we can't have an upper bound shard, we return
+		 * INVALID_SHARD_INDEX here.
+		 */
 		return INVALID_SHARD_INDEX;
 	}
 
-	/* value falls inbetween intervals, return the inverval one smaller as bound */
+	/*
+	 * partitionColumnValue is either greater than all the shards or falls in
+	 * between two shards, which corresponds to possibility 2) or 4).
+	 * Knowing that upperBoundIndex is an exclusive index, we return the index
+	 * for the previous shard here.
+	 */
 	return upperBoundIndex - 1;
 }
 

src/backend/distributed/sql/citus--9.4-1--9.4-2.sql

@@ -0,0 +1,3 @@
+-- 9.4-1--9.4-2 was added later as a patch to fix a bug in our PG upgrade functions
+#include "udfs/citus_prepare_pg_upgrade/9.4-2.sql"
+#include "udfs/citus_finish_pg_upgrade/9.4-2.sql"

src/backend/distributed/sql/citus--9.4-2--9.4-1.sql

@@ -0,0 +1,9 @@
+--
+-- 9.4-1--9.4-2 was added later as a patch to fix a bug in our PG upgrade functions
+--
+-- This script brings users who installed the patch released back to the 9.4-1
+-- upgrade path. We do this via a semantical downgrade since there has already been
+-- introduced new changes in the schema from 9.4-1 to 9.5-1. To make sure we include all
+-- changes made during that version change we decide to use the existing upgrade path from
+-- our later introduced 9.4-2 version.
+--

src/backend/distributed/sql/citus--9.4-2--9.4-3.sql

@@ -0,0 +1,7 @@
+-- 9.4-2--9.4-3 was added later as a patch to improve master_update_table_statistics
+CREATE OR REPLACE FUNCTION master_update_table_statistics(relation regclass)
+RETURNS VOID
+    LANGUAGE C STRICT
+    AS 'MODULE_PATHNAME', $$citus_update_table_statistics$$;
+COMMENT ON FUNCTION pg_catalog.master_update_table_statistics(regclass)
+	IS 'updates shard statistics of the given table';

src/backend/distributed/sql/citus--9.4-3--9.4-2.sql

@@ -0,0 +1,22 @@
+-- citus--9.4-3--9.4-2
+-- This is a downgrade path that will revert the changes made in citus--9.4-2--9.4-3.sql
+-- 9.4-2--9.4-3 was added later as a patch to improve master_update_table_statistics.
+-- We have this downgrade script so that we can continue from the main upgrade path
+-- when upgrading to later versions.
+CREATE OR REPLACE FUNCTION master_update_table_statistics(relation regclass)
+RETURNS VOID AS $$
+DECLARE
+	colocated_tables regclass[];
+BEGIN
+	SELECT get_colocated_table_array(relation) INTO colocated_tables;
+
+	PERFORM
+		master_update_shard_statistics(shardid)
+	FROM
+		pg_dist_shard
+	WHERE
+		logicalrelid = ANY (colocated_tables);
+END;
+$$ LANGUAGE 'plpgsql';
+COMMENT ON FUNCTION master_update_table_statistics(regclass)
+	IS 'updates shard statistics of the given table and its colocated tables';

src/backend/distributed/sql/citus--9.5-1--9.5-2.sql

@@ -0,0 +1,3 @@
+-- 9.5-1--9.5-2 was added later as a patch to fix a bug in our PG upgrade functions
+#include "udfs/citus_prepare_pg_upgrade/9.5-2.sql"
+#include "udfs/citus_finish_pg_upgrade/9.5-2.sql"

src/backend/distributed/sql/citus--9.5-2--9.5-1.sql

@@ -0,0 +1,9 @@
+--
+-- 9.5-1--9.5-2 was added later as a patch to fix a bug in our PG upgrade functions
+--
+-- This script brings users who installed the patch released back to the 9.5-1
+-- upgrade path. We do this via a semantical downgrade since there has already been
+-- introduced new changes in the schema from 9.5-1 to 10.0-1. To make sure we include all
+-- changes made during that version change we decide to use the existing upgrade path from
+-- our later introduced 9.5-1 version.
+--

src/backend/distributed/sql/citus--9.5-2--9.5-3.sql

@@ -0,0 +1,7 @@
+-- 9.5-2--9.5-3 was added later as a patch to improve master_update_table_statistics
+CREATE OR REPLACE FUNCTION master_update_table_statistics(relation regclass)
+RETURNS VOID
+    LANGUAGE C STRICT
+    AS 'MODULE_PATHNAME', $$citus_update_table_statistics$$;
+COMMENT ON FUNCTION pg_catalog.master_update_table_statistics(regclass)
+	IS 'updates shard statistics of the given table';

src/backend/distributed/sql/citus--9.5-3--9.5-2.sql

@@ -0,0 +1,22 @@
+-- citus--9.5-3--9.5-2
+-- This is a downgrade path that will revert the changes made in citus--9.5-2--9.5-3.sql
+-- 9.5-2--9.5-3 was added later as a patch to improve master_update_table_statistics.
+-- We have this downgrade script so that we can continue from the main upgrade path
+-- when upgrading to later versions.
+CREATE OR REPLACE FUNCTION master_update_table_statistics(relation regclass)
+RETURNS VOID AS $$
+DECLARE
+	colocated_tables regclass[];
+BEGIN
+	SELECT get_colocated_table_array(relation) INTO colocated_tables;
+
+	PERFORM
+		master_update_shard_statistics(shardid)
+	FROM
+		pg_dist_shard
+	WHERE
+		logicalrelid = ANY (colocated_tables);
+END;
+$$ LANGUAGE 'plpgsql';
+COMMENT ON FUNCTION master_update_table_statistics(regclass)
+	IS 'updates shard statistics of the given table and its colocated tables';

src/backend/distributed/sql/udfs/citus_finish_pg_upgrade/9.4-2.sql

@@ -0,0 +1,105 @@
+CREATE OR REPLACE FUNCTION pg_catalog.citus_finish_pg_upgrade()
+    RETURNS void
+    LANGUAGE plpgsql
+    SET search_path = pg_catalog
+    AS $cppu$
+DECLARE
+    table_name regclass;
+    command text;
+    trigger_name text;
+BEGIN
+    --
+    -- restore citus catalog tables
+    --
+    INSERT INTO pg_catalog.pg_dist_partition SELECT * FROM public.pg_dist_partition;
+    INSERT INTO pg_catalog.pg_dist_shard SELECT * FROM public.pg_dist_shard;
+    INSERT INTO pg_catalog.pg_dist_placement SELECT * FROM public.pg_dist_placement;
+    INSERT INTO pg_catalog.pg_dist_node_metadata SELECT * FROM public.pg_dist_node_metadata;
+    INSERT INTO pg_catalog.pg_dist_node SELECT * FROM public.pg_dist_node;
+    INSERT INTO pg_catalog.pg_dist_local_group SELECT * FROM public.pg_dist_local_group;
+    INSERT INTO pg_catalog.pg_dist_transaction SELECT * FROM public.pg_dist_transaction;
+    INSERT INTO pg_catalog.pg_dist_colocation SELECT * FROM public.pg_dist_colocation;
+    -- enterprise catalog tables
+    INSERT INTO pg_catalog.pg_dist_authinfo SELECT * FROM public.pg_dist_authinfo;
+    INSERT INTO pg_catalog.pg_dist_poolinfo SELECT * FROM public.pg_dist_poolinfo;
+
+    ALTER TABLE pg_catalog.pg_dist_rebalance_strategy DISABLE TRIGGER pg_dist_rebalance_strategy_enterprise_check_trigger;
+    INSERT INTO pg_catalog.pg_dist_rebalance_strategy SELECT
+        name,
+        default_strategy,
+        shard_cost_function::regprocedure::regproc,
+        node_capacity_function::regprocedure::regproc,
+        shard_allowed_on_node_function::regprocedure::regproc,
+        default_threshold,
+        minimum_threshold
+    FROM public.pg_dist_rebalance_strategy;
+    ALTER TABLE pg_catalog.pg_dist_rebalance_strategy ENABLE TRIGGER pg_dist_rebalance_strategy_enterprise_check_trigger;
+
+    --
+    -- drop backup tables
+    --
+    DROP TABLE public.pg_dist_authinfo;
+    DROP TABLE public.pg_dist_colocation;
+    DROP TABLE public.pg_dist_local_group;
+    DROP TABLE public.pg_dist_node;
+    DROP TABLE public.pg_dist_node_metadata;
+    DROP TABLE public.pg_dist_partition;
+    DROP TABLE public.pg_dist_placement;
+    DROP TABLE public.pg_dist_poolinfo;
+    DROP TABLE public.pg_dist_shard;
+    DROP TABLE public.pg_dist_transaction;
+
+    --
+    -- reset sequences
+    --
+    PERFORM setval('pg_catalog.pg_dist_shardid_seq', (SELECT MAX(shardid)+1 AS max_shard_id FROM pg_dist_shard), false);
+    PERFORM setval('pg_catalog.pg_dist_placement_placementid_seq', (SELECT MAX(placementid)+1 AS max_placement_id FROM pg_dist_placement), false);
+    PERFORM setval('pg_catalog.pg_dist_groupid_seq', (SELECT MAX(groupid)+1 AS max_group_id FROM pg_dist_node), false);
+    PERFORM setval('pg_catalog.pg_dist_node_nodeid_seq', (SELECT MAX(nodeid)+1 AS max_node_id FROM pg_dist_node), false);
+    PERFORM setval('pg_catalog.pg_dist_colocationid_seq', (SELECT MAX(colocationid)+1 AS max_colocation_id FROM pg_dist_colocation), false);
+
+    --
+    -- register triggers
+    --
+    FOR table_name IN SELECT logicalrelid FROM pg_catalog.pg_dist_partition
+    LOOP
+        trigger_name := 'truncate_trigger_' || table_name::oid;
+        command := 'create trigger ' || trigger_name || ' after truncate on ' || table_name || ' execute procedure pg_catalog.citus_truncate_trigger()';
+        EXECUTE command;
+        command := 'update pg_trigger set tgisinternal = true where tgname = ' || quote_literal(trigger_name);
+        EXECUTE command;
+    END LOOP;
+
+    --
+    -- set dependencies
+    --
+    INSERT INTO pg_depend
+    SELECT
+        'pg_class'::regclass::oid as classid,
+        p.logicalrelid::regclass::oid as objid,
+        0 as objsubid,
+        'pg_extension'::regclass::oid as refclassid,
+        (select oid from pg_extension where extname = 'citus') as refobjid,
+        0 as refobjsubid ,
+        'n' as deptype
+    FROM pg_catalog.pg_dist_partition p;
+
+    -- restore pg_dist_object from the stable identifiers
+    TRUNCATE citus.pg_dist_object;
+    INSERT INTO citus.pg_dist_object (classid, objid, objsubid, distribution_argument_index, colocationid)
+    SELECT
+        address.classid,
+        address.objid,
+        address.objsubid,
+        naming.distribution_argument_index,
+        naming.colocationid
+    FROM
+        public.pg_dist_object naming,
+        pg_catalog.pg_get_object_address(naming.type, naming.object_names, naming.object_args) address;
+
+    DROP TABLE public.pg_dist_object;
+END;
+$cppu$;
+
+COMMENT ON FUNCTION pg_catalog.citus_finish_pg_upgrade()
+    IS 'perform tasks to restore citus settings from a location that has been prepared before pg_upgrade';

src/backend/distributed/sql/udfs/citus_finish_pg_upgrade/9.5-2.sql

@@ -0,0 +1,106 @@
+CREATE OR REPLACE FUNCTION pg_catalog.citus_finish_pg_upgrade()
+    RETURNS void
+    LANGUAGE plpgsql
+    SET search_path = pg_catalog
+    AS $cppu$
+DECLARE
+    table_name regclass;
+    command text;
+    trigger_name text;
+BEGIN
+    --
+    -- restore citus catalog tables
+    --
+    INSERT INTO pg_catalog.pg_dist_partition SELECT * FROM public.pg_dist_partition;
+    INSERT INTO pg_catalog.pg_dist_shard SELECT * FROM public.pg_dist_shard;
+    INSERT INTO pg_catalog.pg_dist_placement SELECT * FROM public.pg_dist_placement;
+    INSERT INTO pg_catalog.pg_dist_node_metadata SELECT * FROM public.pg_dist_node_metadata;
+    INSERT INTO pg_catalog.pg_dist_node SELECT * FROM public.pg_dist_node;
+    INSERT INTO pg_catalog.pg_dist_local_group SELECT * FROM public.pg_dist_local_group;
+    INSERT INTO pg_catalog.pg_dist_transaction SELECT * FROM public.pg_dist_transaction;
+    INSERT INTO pg_catalog.pg_dist_colocation SELECT * FROM public.pg_dist_colocation;
+    -- enterprise catalog tables
+    INSERT INTO pg_catalog.pg_dist_authinfo SELECT * FROM public.pg_dist_authinfo;
+    INSERT INTO pg_catalog.pg_dist_poolinfo SELECT * FROM public.pg_dist_poolinfo;
+
+    ALTER TABLE pg_catalog.pg_dist_rebalance_strategy DISABLE TRIGGER pg_dist_rebalance_strategy_enterprise_check_trigger;
+    INSERT INTO pg_catalog.pg_dist_rebalance_strategy SELECT
+        name,
+        default_strategy,
+        shard_cost_function::regprocedure::regproc,
+        node_capacity_function::regprocedure::regproc,
+        shard_allowed_on_node_function::regprocedure::regproc,
+        default_threshold,
+        minimum_threshold
+    FROM public.pg_dist_rebalance_strategy;
+    ALTER TABLE pg_catalog.pg_dist_rebalance_strategy ENABLE TRIGGER pg_dist_rebalance_strategy_enterprise_check_trigger;
+
+    --
+    -- drop backup tables
+    --
+    DROP TABLE public.pg_dist_authinfo;
+    DROP TABLE public.pg_dist_colocation;
+    DROP TABLE public.pg_dist_local_group;
+    DROP TABLE public.pg_dist_node;
+    DROP TABLE public.pg_dist_node_metadata;
+    DROP TABLE public.pg_dist_partition;
+    DROP TABLE public.pg_dist_placement;
+    DROP TABLE public.pg_dist_poolinfo;
+    DROP TABLE public.pg_dist_shard;
+    DROP TABLE public.pg_dist_transaction;
+    DROP TABLE public.pg_dist_rebalance_strategy;
+
+    --
+    -- reset sequences
+    --
+    PERFORM setval('pg_catalog.pg_dist_shardid_seq', (SELECT MAX(shardid)+1 AS max_shard_id FROM pg_dist_shard), false);
+    PERFORM setval('pg_catalog.pg_dist_placement_placementid_seq', (SELECT MAX(placementid)+1 AS max_placement_id FROM pg_dist_placement), false);
+    PERFORM setval('pg_catalog.pg_dist_groupid_seq', (SELECT MAX(groupid)+1 AS max_group_id FROM pg_dist_node), false);
+    PERFORM setval('pg_catalog.pg_dist_node_nodeid_seq', (SELECT MAX(nodeid)+1 AS max_node_id FROM pg_dist_node), false);
+    PERFORM setval('pg_catalog.pg_dist_colocationid_seq', (SELECT MAX(colocationid)+1 AS max_colocation_id FROM pg_dist_colocation), false);
+
+    --
+    -- register triggers
+    --
+    FOR table_name IN SELECT logicalrelid FROM pg_catalog.pg_dist_partition
+    LOOP
+        trigger_name := 'truncate_trigger_' || table_name::oid;
+        command := 'create trigger ' || trigger_name || ' after truncate on ' || table_name || ' execute procedure pg_catalog.citus_truncate_trigger()';
+        EXECUTE command;
+        command := 'update pg_trigger set tgisinternal = true where tgname = ' || quote_literal(trigger_name);
+        EXECUTE command;
+    END LOOP;
+
+    --
+    -- set dependencies
+    --
+    INSERT INTO pg_depend
+    SELECT
+        'pg_class'::regclass::oid as classid,
+        p.logicalrelid::regclass::oid as objid,
+        0 as objsubid,
+        'pg_extension'::regclass::oid as refclassid,
+        (select oid from pg_extension where extname = 'citus') as refobjid,
+        0 as refobjsubid ,
+        'n' as deptype
+    FROM pg_catalog.pg_dist_partition p;
+
+    -- restore pg_dist_object from the stable identifiers
+    TRUNCATE citus.pg_dist_object;
+    INSERT INTO citus.pg_dist_object (classid, objid, objsubid, distribution_argument_index, colocationid)
+    SELECT
+        address.classid,
+        address.objid,
+        address.objsubid,
+        naming.distribution_argument_index,
+        naming.colocationid
+    FROM
+        public.pg_dist_object naming,
+        pg_catalog.pg_get_object_address(naming.type, naming.object_names, naming.object_args) address;
+
+    DROP TABLE public.pg_dist_object;
+END;
+$cppu$;
+
+COMMENT ON FUNCTION pg_catalog.citus_finish_pg_upgrade()
+    IS 'perform tasks to restore citus settings from a location that has been prepared before pg_upgrade';

src/backend/distributed/sql/udfs/citus_finish_pg_upgrade/latest.sql

@@ -86,17 +86,7 @@ BEGIN
     FROM pg_catalog.pg_dist_partition p;
 
     -- restore pg_dist_object from the stable identifiers
-    -- DELETE/INSERT to avoid primary key violations
-    WITH old_records AS (
-        DELETE FROM
-            citus.pg_dist_object
-        RETURNING
-            type,
-            object_names,
-            object_args,
-            distribution_argument_index,
-            colocationid
-    )
+    TRUNCATE citus.pg_dist_object;
     INSERT INTO citus.pg_dist_object (classid, objid, objsubid, distribution_argument_index, colocationid)
     SELECT
         address.classid,
@@ -105,8 +95,10 @@ BEGIN
         naming.distribution_argument_index,
         naming.colocationid
     FROM
-        old_records naming,
-        pg_get_object_address(naming.type, naming.object_names, naming.object_args) address;
+        public.pg_dist_object naming,
+        pg_catalog.pg_get_object_address(naming.type, naming.object_names, naming.object_args) address;
+
+    DROP TABLE public.pg_dist_object;
 END;
 $cppu$;
 

src/backend/distributed/sql/udfs/citus_prepare_pg_upgrade/9.4-2.sql

@@ -0,0 +1,44 @@
+CREATE OR REPLACE FUNCTION pg_catalog.citus_prepare_pg_upgrade()
+    RETURNS void
+    LANGUAGE plpgsql
+    SET search_path = pg_catalog
+    AS $cppu$
+BEGIN
+    --
+    -- backup citus catalog tables
+    --
+    CREATE TABLE public.pg_dist_partition AS SELECT * FROM pg_catalog.pg_dist_partition;
+    CREATE TABLE public.pg_dist_shard AS SELECT * FROM pg_catalog.pg_dist_shard;
+    CREATE TABLE public.pg_dist_placement AS SELECT * FROM pg_catalog.pg_dist_placement;
+    CREATE TABLE public.pg_dist_node_metadata AS SELECT * FROM pg_catalog.pg_dist_node_metadata;
+    CREATE TABLE public.pg_dist_node AS SELECT * FROM pg_catalog.pg_dist_node;
+    CREATE TABLE public.pg_dist_local_group AS SELECT * FROM pg_catalog.pg_dist_local_group;
+    CREATE TABLE public.pg_dist_transaction AS SELECT * FROM pg_catalog.pg_dist_transaction;
+    CREATE TABLE public.pg_dist_colocation AS SELECT * FROM pg_catalog.pg_dist_colocation;
+    -- enterprise catalog tables
+    CREATE TABLE public.pg_dist_authinfo AS SELECT * FROM pg_catalog.pg_dist_authinfo;
+    CREATE TABLE public.pg_dist_poolinfo AS SELECT * FROM pg_catalog.pg_dist_poolinfo;
+    CREATE TABLE public.pg_dist_rebalance_strategy AS SELECT
+        name,
+        default_strategy,
+        shard_cost_function::regprocedure::text,
+        node_capacity_function::regprocedure::text,
+        shard_allowed_on_node_function::regprocedure::text,
+        default_threshold,
+        minimum_threshold
+    FROM pg_catalog.pg_dist_rebalance_strategy;
+
+    -- store upgrade stable identifiers on pg_dist_object catalog
+    CREATE TABLE public.pg_dist_object AS SELECT
+       address.type,
+       address.object_names,
+       address.object_args,
+       objects.distribution_argument_index,
+       objects.colocationid
+    FROM citus.pg_dist_object objects,
+         pg_catalog.pg_identify_object_as_address(objects.classid, objects.objid, objects.objsubid) address;
+END;
+$cppu$;
+
+COMMENT ON FUNCTION pg_catalog.citus_prepare_pg_upgrade()
+    IS 'perform tasks to copy citus settings to a location that could later be restored after pg_upgrade is done';

src/backend/distributed/sql/udfs/citus_prepare_pg_upgrade/9.5-2.sql

@@ -0,0 +1,60 @@
+CREATE OR REPLACE FUNCTION pg_catalog.citus_prepare_pg_upgrade()
+    RETURNS void
+    LANGUAGE plpgsql
+    SET search_path = pg_catalog
+    AS $cppu$
+BEGIN
+    --
+    -- Drop existing backup tables
+    --
+    DROP TABLE IF EXISTS public.pg_dist_partition;
+    DROP TABLE IF EXISTS public.pg_dist_shard;
+    DROP TABLE IF EXISTS public.pg_dist_placement;
+    DROP TABLE IF EXISTS public.pg_dist_node_metadata;
+    DROP TABLE IF EXISTS public.pg_dist_node;
+    DROP TABLE IF EXISTS public.pg_dist_local_group;
+    DROP TABLE IF EXISTS public.pg_dist_transaction;
+    DROP TABLE IF EXISTS public.pg_dist_colocation;
+    DROP TABLE IF EXISTS public.pg_dist_authinfo;
+    DROP TABLE IF EXISTS public.pg_dist_poolinfo;
+    DROP TABLE IF EXISTS public.pg_dist_rebalance_strategy;
+    DROP TABLE IF EXISTS public.pg_dist_object;
+
+    --
+    -- backup citus catalog tables
+    --
+    CREATE TABLE public.pg_dist_partition AS SELECT * FROM pg_catalog.pg_dist_partition;
+    CREATE TABLE public.pg_dist_shard AS SELECT * FROM pg_catalog.pg_dist_shard;
+    CREATE TABLE public.pg_dist_placement AS SELECT * FROM pg_catalog.pg_dist_placement;
+    CREATE TABLE public.pg_dist_node_metadata AS SELECT * FROM pg_catalog.pg_dist_node_metadata;
+    CREATE TABLE public.pg_dist_node AS SELECT * FROM pg_catalog.pg_dist_node;
+    CREATE TABLE public.pg_dist_local_group AS SELECT * FROM pg_catalog.pg_dist_local_group;
+    CREATE TABLE public.pg_dist_transaction AS SELECT * FROM pg_catalog.pg_dist_transaction;
+    CREATE TABLE public.pg_dist_colocation AS SELECT * FROM pg_catalog.pg_dist_colocation;
+    -- enterprise catalog tables
+    CREATE TABLE public.pg_dist_authinfo AS SELECT * FROM pg_catalog.pg_dist_authinfo;
+    CREATE TABLE public.pg_dist_poolinfo AS SELECT * FROM pg_catalog.pg_dist_poolinfo;
+    CREATE TABLE public.pg_dist_rebalance_strategy AS SELECT
+        name,
+        default_strategy,
+        shard_cost_function::regprocedure::text,
+        node_capacity_function::regprocedure::text,
+        shard_allowed_on_node_function::regprocedure::text,
+        default_threshold,
+        minimum_threshold
+    FROM pg_catalog.pg_dist_rebalance_strategy;
+
+    -- store upgrade stable identifiers on pg_dist_object catalog
+    CREATE TABLE public.pg_dist_object AS SELECT
+       address.type,
+       address.object_names,
+       address.object_args,
+       objects.distribution_argument_index,
+       objects.colocationid
+    FROM citus.pg_dist_object objects,
+         pg_catalog.pg_identify_object_as_address(objects.classid, objects.objid, objects.objsubid) address;
+END;
+$cppu$;
+
+COMMENT ON FUNCTION pg_catalog.citus_prepare_pg_upgrade()
+    IS 'perform tasks to copy citus settings to a location that could later be restored after pg_upgrade is done';

src/backend/distributed/sql/udfs/citus_prepare_pg_upgrade/latest.sql

@@ -18,6 +18,7 @@ BEGIN
     DROP TABLE IF EXISTS public.pg_dist_authinfo;
     DROP TABLE IF EXISTS public.pg_dist_poolinfo;
     DROP TABLE IF EXISTS public.pg_dist_rebalance_strategy;
+    DROP TABLE IF EXISTS public.pg_dist_object;
 
     --
     -- backup citus catalog tables
@@ -44,8 +45,14 @@ BEGIN
     FROM pg_catalog.pg_dist_rebalance_strategy;
 
     -- store upgrade stable identifiers on pg_dist_object catalog
-    UPDATE citus.pg_dist_object
-       SET (type, object_names, object_args) = (SELECT * FROM pg_identify_object_as_address(classid, objid, objsubid));
+    CREATE TABLE public.pg_dist_object AS SELECT
+       address.type,
+       address.object_names,
+       address.object_args,
+       objects.distribution_argument_index,
+       objects.colocationid
+    FROM citus.pg_dist_object objects,
+         pg_catalog.pg_identify_object_as_address(objects.classid, objects.objid, objects.objsubid) address;
 END;
 $cppu$;
 

src/backend/distributed/test/metadata_sync.c

@@ -16,6 +16,7 @@
 #include "catalog/pg_type.h"
 #include "distributed/connection_management.h"
 #include "distributed/listutils.h"
+#include "distributed/maintenanced.h"
 #include "distributed/metadata_sync.h"
 #include "distributed/remote_commands.h"
 #include "postmaster/postmaster.h"
@@ -28,6 +29,8 @@
 /* declarations for dynamic loading */
 PG_FUNCTION_INFO_V1(master_metadata_snapshot);
 PG_FUNCTION_INFO_V1(wait_until_metadata_sync);
+PG_FUNCTION_INFO_V1(trigger_metadata_sync);
+PG_FUNCTION_INFO_V1(raise_error_in_metadata_sync);
 
 
 /*
@@ -124,3 +127,26 @@ wait_until_metadata_sync(PG_FUNCTION_ARGS)
 
 	PG_RETURN_VOID();
 }
+
+
+/*
+ * trigger_metadata_sync triggers metadata sync for testing.
+ */
+Datum
+trigger_metadata_sync(PG_FUNCTION_ARGS)
+{
+	TriggerMetadataSyncOnCommit();
+	PG_RETURN_VOID();
+}
+
+
+/*
+ * raise_error_in_metadata_sync causes metadata sync to raise an error.
+ */
+Datum
+raise_error_in_metadata_sync(PG_FUNCTION_ARGS)
+{
+	/* metadata sync uses SIGALRM to test errors */
+	SignalMetadataSyncDaemon(MyDatabaseId, SIGALRM);
+	PG_RETURN_VOID();
+}

src/backend/distributed/transaction/transaction_management.c

@@ -28,6 +28,7 @@
 #include "distributed/listutils.h"
 #include "distributed/local_executor.h"
 #include "distributed/locally_reserved_shared_connections.h"
+#include "distributed/maintenanced.h"
 #include "distributed/multi_executor.h"
 #include "distributed/multi_explain.h"
 #include "distributed/repartition_join_execution.h"
@@ -102,6 +103,9 @@ bool CoordinatedTransactionUses2PC = false;
 /* if disabled, distributed statements in a function may run as separate transactions */
 bool FunctionOpensTransactionBlock = true;
 
+/* if true, we should trigger metadata sync on commit */
+bool MetadataSyncOnCommit = false;
+
 
 /* transaction management functions */
 static void CoordinatedTransactionCallback(XactEvent event, void *arg);
@@ -262,6 +266,15 @@ CoordinatedTransactionCallback(XactEvent event, void *arg)
 				AfterXactConnectionHandling(true);
 			}
 
+			/*
+			 * Changes to catalog tables are now visible to the metadata sync
+			 * daemon, so we can trigger metadata sync if necessary.
+			 */
+			if (MetadataSyncOnCommit)
+			{
+				TriggerMetadataSync(MyDatabaseId);
+			}
+
 			ResetGlobalVariables();
 
 			/*
@@ -474,6 +487,7 @@ ResetGlobalVariables()
 	activeSetStmts = NULL;
 	CoordinatedTransactionUses2PC = false;
 	TransactionModifiedNodeMetadata = false;
+	MetadataSyncOnCommit = false;
 	ResetWorkerErrorIndication();
 }
 
@@ -728,3 +742,15 @@ MaybeExecutingUDF(void)
 {
 	return ExecutorLevel > 1 || (ExecutorLevel == 1 && PlannerLevel > 0);
 }
+
+
+/*
+ * TriggerMetadataSyncOnCommit sets a flag to do metadata sync on commit.
+ * This is because new metadata only becomes visible to the metadata sync
+ * daemon after commit happens.
+ */
+void
+TriggerMetadataSyncOnCommit(void)
+{
+	MetadataSyncOnCommit = true;
+}

src/backend/distributed/utils/distribution_column.c

@@ -18,6 +18,7 @@
 #include "access/htup_details.h"
 #include "distributed/distribution_column.h"
 #include "distributed/metadata_cache.h"
+#include "distributed/multi_partitioning_utils.h"
 #include "distributed/version_compat.h"
 #include "nodes/makefuncs.h"
 #include "nodes/nodes.h"
@@ -115,6 +116,53 @@ column_to_column_name(PG_FUNCTION_ARGS)
 }
 
 
+/*
+ * FindColumnWithNameOnTargetRelation gets a source table and
+ * column name. The function returns the the column with the
+ * same name on the target table.
+ *
+ * Note that due to dropping columns, the parent's distribution key may not
+ * match the partition's distribution key. See issue #5123.
+ *
+ * The function throws error if the input or output is not valid or does
+ * not exist.
+ */
+Var *
+FindColumnWithNameOnTargetRelation(Oid sourceRelationId, char *sourceColumnName,
+								   Oid targetRelationId)
+{
+	if (sourceColumnName == NULL || sourceColumnName[0] == '\0')
+	{
+		ereport(ERROR, (errcode(ERRCODE_UNDEFINED_COLUMN),
+						errmsg("cannot find the given column on table \"%s\"",
+							   generate_qualified_relation_name(sourceRelationId))));
+	}
+
+	AttrNumber attributeNumberOnTarget = get_attnum(targetRelationId, sourceColumnName);
+	if (attributeNumberOnTarget == InvalidAttrNumber)
+	{
+		ereport(ERROR, (errmsg("Column \"%s\" does not exist on "
+							   "relation \"%s\"", sourceColumnName,
+							   get_rel_name(targetRelationId))));
+	}
+
+	Index varNo = 1;
+	Oid targetTypeId = InvalidOid;
+	int32 targetTypMod = 0;
+	Oid targetCollation = InvalidOid;
+	Index varlevelsup = 0;
+
+	/* this function throws error in case anything goes wrong */
+	get_atttypetypmodcoll(targetRelationId, attributeNumberOnTarget,
+						  &targetTypeId, &targetTypMod, &targetCollation);
+	Var *targetColumn =
+		makeVar(varNo, attributeNumberOnTarget, targetTypeId, targetTypMod,
+				targetCollation, varlevelsup);
+
+	return targetColumn;
+}
+
+
 /*
  * BuildDistributionKeyFromColumnName builds a simple distribution key consisting
  * only out of a reference to the column of name columnName. Errors out if the

src/backend/distributed/utils/foreign_key_relationship.c

@@ -58,7 +58,6 @@ typedef struct ForeignConstraintRelationshipGraph
 typedef struct ForeignConstraintRelationshipNode
 {
 	Oid relationId;
-	bool visited;
 	List *adjacencyList;
 	List *backAdjacencyList;
 }ForeignConstraintRelationshipNode;
@@ -78,16 +77,21 @@ typedef struct ForeignConstraintRelationshipEdge
 
 static ForeignConstraintRelationshipGraph *fConstraintRelationshipGraph = NULL;
 
+static ForeignConstraintRelationshipNode * GetRelationshipNodeForRelationId(Oid
+																			relationId,
+																			bool *isFound);
 static void CreateForeignConstraintRelationshipGraph(void);
+static List * GetNeighbourList(ForeignConstraintRelationshipNode *relationshipNode,
+							   bool isReferencing);
+static List * GetRelationIdsFromRelationshipNodeList(List *fKeyRelationshipNodeList);
 static void PopulateAdjacencyLists(void);
 static int CompareForeignConstraintRelationshipEdges(const void *leftElement,
 													 const void *rightElement);
 static void AddForeignConstraintRelationshipEdge(Oid referencingOid, Oid referencedOid);
 static ForeignConstraintRelationshipNode * CreateOrFindNode(HTAB *adjacencyLists, Oid
 															relid);
-static void GetConnectedListHelper(ForeignConstraintRelationshipNode *node,
-								   List **adjacentNodeList, bool
-								   isReferencing);
+static List * GetConnectedListHelper(ForeignConstraintRelationshipNode *node,
+									 bool isReferencing);
 static List * GetForeignConstraintRelationshipHelper(Oid relationId, bool isReferencing);
 
 
@@ -108,7 +112,7 @@ ReferencedRelationIdList(Oid relationId)
 
 /*
  * ReferencingRelationIdList is a wrapper function around GetForeignConstraintRelationshipHelper
- * to get list of relation IDs which are referencing by the given relation id.
+ * to get list of relation IDs which are referencing to given relation id.
  *
  * Note that, if relation A is referenced by relation B and relation B is referenced
  * by relation C, then the result list for relation C consists of the relation
@@ -129,16 +133,9 @@ ReferencingRelationIdList(Oid relationId)
 static List *
 GetForeignConstraintRelationshipHelper(Oid relationId, bool isReferencing)
 {
-	List *foreignConstraintList = NIL;
-	List *foreignNodeList = NIL;
 	bool isFound = false;
-
-	CreateForeignConstraintRelationshipGraph();
-
-	ForeignConstraintRelationshipNode *relationNode =
-		(ForeignConstraintRelationshipNode *) hash_search(
-			fConstraintRelationshipGraph->nodeMap, &relationId,
-			HASH_FIND, &isFound);
+	ForeignConstraintRelationshipNode *relationshipNode =
+		GetRelationshipNodeForRelationId(relationId, &isFound);
 
 	if (!isFound)
 	{
@@ -149,24 +146,31 @@ GetForeignConstraintRelationshipHelper(Oid relationId, bool isReferencing)
 		return NIL;
 	}
 
-	GetConnectedListHelper(relationNode, &foreignNodeList, isReferencing);
+	List *connectedNodeList = GetConnectedListHelper(relationshipNode, isReferencing);
+	List *relationIdList = GetRelationIdsFromRelationshipNodeList(connectedNodeList);
+	return relationIdList;
+}
 
-	/*
-	 * We need only their OIDs, we get back node list to make their visited
-	 * variable to false for using them iteratively.
-	 */
-	ForeignConstraintRelationshipNode *currentNode = NULL;
-	foreach_ptr(currentNode, foreignNodeList)
-	{
-		foreignConstraintList = lappend_oid(foreignConstraintList,
-											currentNode->relationId);
-		currentNode->visited = false;
-	}
 
-	/* set to false separately, since we don't add itself to foreign node list */
-	relationNode->visited = false;
+/*
+ * GetRelationshipNodeForRelationId searches foreign key graph for relation
+ * with relationId and returns ForeignConstraintRelationshipNode object for
+ * relation if it exists in graph. Otherwise, sets isFound to false.
+ *
+ * Also before searching foreign key graph, this function implicitly builds
+ * foreign key graph if it's invalid or not built yet.
+ */
+static ForeignConstraintRelationshipNode *
+GetRelationshipNodeForRelationId(Oid relationId, bool *isFound)
+{
+	CreateForeignConstraintRelationshipGraph();
 
-	return foreignConstraintList;
+	ForeignConstraintRelationshipNode *relationshipNode =
+		(ForeignConstraintRelationshipNode *) hash_search(
+			fConstraintRelationshipGraph->nodeMap, &relationId,
+			HASH_FIND, isFound);
+
+	return relationshipNode;
 }
 
 
@@ -249,38 +253,142 @@ SetForeignConstraintRelationshipGraphInvalid()
 
 
 /*
- * GetConnectedListHelper is the function for getting nodes connected (or connecting) to
- * the given relation. adjacentNodeList holds the result for recursive calls and
- * by changing isReferencing caller function can select connected or connecting
- * adjacency list.
+ * GetConnectedListHelper returns list of ForeignConstraintRelationshipNode
+ * objects for relations referenced by or referencing to given relation
+ * according to isReferencing flag.
  *
  */
-static void
-GetConnectedListHelper(ForeignConstraintRelationshipNode *node, List **adjacentNodeList,
-					   bool isReferencing)
+static List *
+GetConnectedListHelper(ForeignConstraintRelationshipNode *node, bool isReferencing)
 {
-	List *neighbourList = NIL;
+	HTAB *oidVisitedMap = CreateOidVisitedHashSet();
 
-	node->visited = true;
+	List *connectedNodeList = NIL;
 
+	List *relationshipNodeStack = list_make1(node);
+	while (list_length(relationshipNodeStack) != 0)
+	{
+		/*
+		 * Note that this loop considers leftmost element of
+		 * relationshipNodeStack as top of the stack.
+		 */
+
+		/* pop top element from stack */
+		ForeignConstraintRelationshipNode *currentNode = linitial(relationshipNodeStack);
+		relationshipNodeStack = list_delete_first(relationshipNodeStack);
+
+		Oid currentRelationId = currentNode->relationId;
+		if (!OidVisited(oidVisitedMap, currentRelationId))
+		{
+			connectedNodeList = lappend(connectedNodeList, currentNode);
+			VisitOid(oidVisitedMap, currentRelationId);
+		}
+
+		List *neighbourList = GetNeighbourList(currentNode, isReferencing);
+		ForeignConstraintRelationshipNode *neighbourNode = NULL;
+		foreach_ptr(neighbourNode, neighbourList)
+		{
+			Oid neighbourRelationId = neighbourNode->relationId;
+			if (!OidVisited(oidVisitedMap, neighbourRelationId))
+			{
+				/* push to stack */
+				relationshipNodeStack = lcons(neighbourNode, relationshipNodeStack);
+			}
+		}
+	}
+
+	hash_destroy(oidVisitedMap);
+
+	/* finally remove yourself from list */
+	connectedNodeList = list_delete_first(connectedNodeList);
+	return connectedNodeList;
+}
+
+
+/*
+ * CreateOidVisitedHashSet creates and returns an hash-set object in
+ * CurrentMemoryContext to store visited oid's.
+ * As hash_create allocates memory in heap, callers are responsible to call
+ * hash_destroy when appropriate.
+ */
+HTAB *
+CreateOidVisitedHashSet(void)
+{
+	HASHCTL info = { 0 };
+
+	info.keysize = sizeof(Oid);
+	info.hash = oid_hash;
+	info.hcxt = CurrentMemoryContext;
+
+	/* we don't have value field as it's a set */
+	info.entrysize = info.keysize;
+
+	uint32 hashFlags = (HASH_ELEM | HASH_FUNCTION | HASH_CONTEXT);
+
+	HTAB *oidVisitedMap = hash_create("oid visited hash map", 32, &info, hashFlags);
+	return oidVisitedMap;
+}
+
+
+/*
+ * OidVisited returns true if given oid is visited according to given oid hash-set.
+ */
+bool
+OidVisited(HTAB *oidVisitedMap, Oid oid)
+{
+	bool found = false;
+	hash_search(oidVisitedMap, &oid, HASH_FIND, &found);
+	return found;
+}
+
+
+/*
+ * VisitOid sets given oid as visited in given hash-set.
+ */
+void
+VisitOid(HTAB *oidVisitedMap, Oid oid)
+{
+	bool found = false;
+	hash_search(oidVisitedMap, &oid, HASH_ENTER, &found);
+}
+
+
+/*
+ * GetNeighbourList returns copy of relevant adjacency list of given
+ * ForeignConstraintRelationshipNode object depending on the isReferencing
+ * flag.
+ */
+static List *
+GetNeighbourList(ForeignConstraintRelationshipNode *relationshipNode, bool isReferencing)
+{
 	if (isReferencing)
 	{
-		neighbourList = node->backAdjacencyList;
+		return relationshipNode->backAdjacencyList;
 	}
 	else
 	{
-		neighbourList = node->adjacencyList;
+		return relationshipNode->adjacencyList;
+	}
+}
+
+
+/*
+ * GetRelationIdsFromRelationshipNodeList returns list of relationId's for
+ * given ForeignConstraintRelationshipNode object list.
+ */
+static List *
+GetRelationIdsFromRelationshipNodeList(List *fKeyRelationshipNodeList)
+{
+	List *relationIdList = NIL;
+
+	ForeignConstraintRelationshipNode *fKeyRelationshipNode = NULL;
+	foreach_ptr(fKeyRelationshipNode, fKeyRelationshipNodeList)
+	{
+		Oid relationId = fKeyRelationshipNode->relationId;
+		relationIdList = lappend_oid(relationIdList, relationId);
 	}
 
-	ForeignConstraintRelationshipNode *neighborNode = NULL;
-	foreach_ptr(neighborNode, neighbourList)
-	{
-		if (neighborNode->visited == false)
-		{
-			*adjacentNodeList = lappend(*adjacentNodeList, neighborNode);
-			GetConnectedListHelper(neighborNode, adjacentNodeList, isReferencing);
-		}
-	}
+	return relationIdList;
 }
 
 
@@ -415,7 +523,6 @@ CreateOrFindNode(HTAB *adjacencyLists, Oid relid)
 	{
 		node->adjacencyList = NIL;
 		node->backAdjacencyList = NIL;
-		node->visited = false;
 	}
 
 	return node;

src/backend/distributed/utils/maintenanced.c

@@ -118,7 +118,6 @@ static size_t MaintenanceDaemonShmemSize(void);
 static void MaintenanceDaemonShmemInit(void);
 static void MaintenanceDaemonShmemExit(int code, Datum arg);
 static void MaintenanceDaemonErrorContext(void *arg);
-static bool LockCitusExtension(void);
 static bool MetadataSyncTriggeredCheckAndReset(MaintenanceDaemonDBData *dbData);
 static void WarnMaintenanceDaemonNotStarted(void);
 
@@ -291,6 +290,13 @@ CitusMaintenanceDaemonMain(Datum main_arg)
 	TimestampTz lastRecoveryTime = 0;
 	TimestampTz nextMetadataSyncTime = 0;
 
+
+	/*
+	 * We do metadata sync in a separate background worker. We need its
+	 * handle to be able to check its status.
+	 */
+	BackgroundWorkerHandle *metadataSyncBgwHandle = NULL;
+
 	/*
 	 * Look up this worker's configuration.
 	 */
@@ -371,6 +377,12 @@ CitusMaintenanceDaemonMain(Datum main_arg)
 	/* make worker recognizable in pg_stat_activity */
 	pgstat_report_appname("Citus Maintenance Daemon");
 
+	/*
+	 * Terminate orphaned metadata sync daemons spawned from previously terminated
+	 * or crashed maintenanced instances.
+	 */
+	SignalMetadataSyncDaemon(databaseOid, SIGTERM);
+
 	/* enter main loop */
 	while (!got_SIGTERM)
 	{
@@ -450,21 +462,42 @@ CitusMaintenanceDaemonMain(Datum main_arg)
 		}
 #endif
 
-		if (!RecoveryInProgress() &&
-			(MetadataSyncTriggeredCheckAndReset(myDbData) ||
-			 GetCurrentTimestamp() >= nextMetadataSyncTime))
+		pid_t metadataSyncBgwPid = 0;
+		BgwHandleStatus metadataSyncStatus =
+			metadataSyncBgwHandle != NULL ?
+			GetBackgroundWorkerPid(metadataSyncBgwHandle, &metadataSyncBgwPid) :
+			BGWH_STOPPED;
+
+		if (metadataSyncStatus != BGWH_STOPPED &&
+			GetCurrentTimestamp() >= nextMetadataSyncTime)
 		{
-			bool metadataSyncFailed = false;
+			/*
+			 * Metadata sync is still running, recheck in a short while.
+			 */
+			int nextTimeout = MetadataSyncRetryInterval;
+			nextMetadataSyncTime =
+				TimestampTzPlusMilliseconds(GetCurrentTimestamp(), nextTimeout);
+			timeout = Min(timeout, nextTimeout);
+		}
+		else if (!RecoveryInProgress() &&
+				 metadataSyncStatus == BGWH_STOPPED &&
+				 (MetadataSyncTriggeredCheckAndReset(myDbData) ||
+				  GetCurrentTimestamp() >= nextMetadataSyncTime))
+		{
+			if (metadataSyncBgwHandle)
+			{
+				TerminateBackgroundWorker(metadataSyncBgwHandle);
+				pfree(metadataSyncBgwHandle);
+				metadataSyncBgwHandle = NULL;
+			}
 
 			InvalidateMetadataSystemCache();
 			StartTransactionCommand();
-
-			/*
-			 * Some functions in ruleutils.c, which we use to get the DDL for
-			 * metadata propagation, require an active snapshot.
-			 */
 			PushActiveSnapshot(GetTransactionSnapshot());
 
+			int nextTimeout = MetadataSyncRetryInterval;
+			bool syncMetadata = false;
+
 			if (!LockCitusExtension())
 			{
 				ereport(DEBUG1, (errmsg("could not lock the citus extension, "
@@ -472,25 +505,28 @@ CitusMaintenanceDaemonMain(Datum main_arg)
 			}
 			else if (CheckCitusVersion(DEBUG1) && CitusHasBeenLoaded())
 			{
-				MetadataSyncResult result = SyncMetadataToNodes();
-				metadataSyncFailed = (result != METADATA_SYNC_SUCCESS);
+				bool lockFailure = false;
+				syncMetadata = ShouldInitiateMetadataSync(&lockFailure);
 
 				/*
-				 * Notification means we had an attempt on synchronization
-				 * without being blocked for pg_dist_node access.
+				 * If lock fails, we need to recheck in a short while. If we are
+				 * going to sync metadata, we should recheck in a short while to
+				 * see if it failed. Otherwise, we can wait longer.
 				 */
-				if (result != METADATA_SYNC_FAILED_LOCK)
-				{
-					Async_Notify(METADATA_SYNC_CHANNEL, NULL);
-				}
+				nextTimeout = (lockFailure || syncMetadata) ?
+							  MetadataSyncRetryInterval :
+							  MetadataSyncInterval;
 			}
 
 			PopActiveSnapshot();
 			CommitTransactionCommand();
-			ProcessCompletedNotifies();
 
-			int64 nextTimeout = metadataSyncFailed ? MetadataSyncRetryInterval :
-								MetadataSyncInterval;
+			if (syncMetadata)
+			{
+				metadataSyncBgwHandle =
+					SpawnSyncMetadataToNodes(MyDatabaseId, myDbData->userOid);
+			}
+
 			nextMetadataSyncTime =
 				TimestampTzPlusMilliseconds(GetCurrentTimestamp(), nextTimeout);
 			timeout = Min(timeout, nextTimeout);
@@ -626,6 +662,11 @@ CitusMaintenanceDaemonMain(Datum main_arg)
 			ProcessConfigFile(PGC_SIGHUP);
 		}
 	}
+
+	if (metadataSyncBgwHandle)
+	{
+		TerminateBackgroundWorker(metadataSyncBgwHandle);
+	}
 }
 
 
@@ -786,7 +827,7 @@ MaintenanceDaemonErrorContext(void *arg)
  * LockCitusExtension acquires a lock on the Citus extension or returns
  * false if the extension does not exist or is being dropped.
  */
-static bool
+bool
 LockCitusExtension(void)
 {
 	Oid extensionOid = get_extension_oid("citus", true);

src/backend/distributed/utils/resource_lock.c

@@ -502,8 +502,6 @@ LockShardResource(uint64 shardId, LOCKMODE lockmode)
 	const bool sessionLock = false;
 	const bool dontWait = false;
 
-	AssertArg(shardId != INVALID_SHARD_ID);
-
 	SET_LOCKTAG_SHARD_RESOURCE(tag, MyDatabaseId, shardId);
 
 	(void) LockAcquire(&tag, lockmode, sessionLock, dontWait);

src/backend/distributed/utils/role.c

@@ -41,7 +41,7 @@ alter_role_if_exists(PG_FUNCTION_ARGS)
 
 	Node *parseTree = ParseTreeNode(utilityQuery);
 
-	CitusProcessUtility(parseTree, utilityQuery, PROCESS_UTILITY_TOPLEVEL, NULL,
+	CitusProcessUtility(parseTree, utilityQuery, PROCESS_UTILITY_QUERY, NULL,
 						None_Receiver, NULL);
 
 	PG_RETURN_BOOL(true);
@@ -98,7 +98,7 @@ worker_create_or_alter_role(PG_FUNCTION_ARGS)
 
 		CitusProcessUtility(parseTree,
 							createRoleUtilityQuery,
-							PROCESS_UTILITY_TOPLEVEL,
+							PROCESS_UTILITY_QUERY,
 							NULL,
 							None_Receiver, NULL);
 
@@ -126,7 +126,7 @@ worker_create_or_alter_role(PG_FUNCTION_ARGS)
 
 		CitusProcessUtility(parseTree,
 							alterRoleUtilityQuery,
-							PROCESS_UTILITY_TOPLEVEL,
+							PROCESS_UTILITY_QUERY,
 							NULL,
 							None_Receiver, NULL);
 

src/backend/distributed/utils/shardinterval_utils.c

@@ -297,7 +297,7 @@ FindShardIntervalIndex(Datum searchedValue, CitusTableCacheEntry *cacheEntry)
 	ShardInterval **shardIntervalCache = cacheEntry->sortedShardIntervalArray;
 	int shardCount = cacheEntry->shardIntervalArrayLength;
 	FmgrInfo *compareFunction = cacheEntry->shardIntervalCompareFunction;
-	bool useBinarySearch = (IsCitusTableTypeCacheEntry(cacheEntry, HASH_DISTRIBUTED) ||
+	bool useBinarySearch = (!IsCitusTableTypeCacheEntry(cacheEntry, HASH_DISTRIBUTED) ||
 							!cacheEntry->hasUniformHashDistribution);
 	int shardIndex = INVALID_SHARD_INDEX;
 
@@ -465,7 +465,7 @@ SingleReplicatedTable(Oid relationId)
 	List *shardPlacementList = NIL;
 
 	/* we could have append/range distributed tables without shards */
-	if (list_length(shardList) <= 1)
+	if (list_length(shardList) == 0)
 	{
 		return false;
 	}

src/backend/distributed/worker/worker_create_or_replace.c

@@ -111,12 +111,12 @@ worker_create_or_replace_object(PG_FUNCTION_ARGS)
 		RenameStmt *renameStmt = CreateRenameStatement(&address, newName);
 		const char *sqlRenameStmt = DeparseTreeNode((Node *) renameStmt);
 		CitusProcessUtility((Node *) renameStmt, sqlRenameStmt,
-							PROCESS_UTILITY_TOPLEVEL,
+							PROCESS_UTILITY_QUERY,
 							NULL, None_Receiver, NULL);
 	}
 
 	/* apply create statement locally */
-	CitusProcessUtility(parseTree, sqlStatement, PROCESS_UTILITY_TOPLEVEL, NULL,
+	CitusProcessUtility(parseTree, sqlStatement, PROCESS_UTILITY_QUERY, NULL,
 						None_Receiver, NULL);
 
 	/* type has been created */

src/backend/distributed/worker/worker_data_fetch_protocol.c

@@ -28,13 +28,14 @@
 #include "commands/extension.h"
 #include "commands/sequence.h"
 #include "distributed/citus_ruleutils.h"
+#include "distributed/commands/multi_copy.h"
 #include "distributed/commands/utility_hook.h"
 #include "distributed/connection_management.h"
-#include "distributed/listutils.h"
 #include "distributed/coordinator_protocol.h"
+#include "distributed/intermediate_results.h"
+#include "distributed/listutils.h"
 #include "distributed/metadata_cache.h"
 #include "distributed/multi_client_executor.h"
-#include "distributed/commands/multi_copy.h"
 #include "distributed/multi_logical_optimizer.h"
 #include "distributed/multi_partitioning_utils.h"
 #include "distributed/multi_server_executor.h"
@@ -45,6 +46,7 @@
 #include "distributed/worker_protocol.h"
 #include "distributed/version_compat.h"
 #include "nodes/makefuncs.h"
+#include "parser/parse_relation.h"
 #include "storage/lmgr.h"
 #include "tcop/tcopprot.h"
 #include "tcop/utility.h"
@@ -396,7 +398,7 @@ worker_apply_shard_ddl_command(PG_FUNCTION_ARGS)
 
 	/* extend names in ddl command and apply extended command */
 	RelayEventExtendNames(ddlCommandNode, schemaName, shardId);
-	CitusProcessUtility(ddlCommandNode, ddlCommand, PROCESS_UTILITY_TOPLEVEL, NULL,
+	CitusProcessUtility(ddlCommandNode, ddlCommand, PROCESS_UTILITY_QUERY, NULL,
 						None_Receiver, NULL);
 
 	PG_RETURN_VOID();
@@ -428,7 +430,7 @@ worker_apply_inter_shard_ddl_command(PG_FUNCTION_ARGS)
 	RelayEventExtendNamesForInterShardCommands(ddlCommandNode, leftShardId,
 											   leftShardSchemaName, rightShardId,
 											   rightShardSchemaName);
-	CitusProcessUtility(ddlCommandNode, ddlCommand, PROCESS_UTILITY_TOPLEVEL, NULL,
+	CitusProcessUtility(ddlCommandNode, ddlCommand, PROCESS_UTILITY_QUERY, NULL,
 						None_Receiver, NULL);
 
 	PG_RETURN_VOID();
@@ -461,7 +463,7 @@ worker_apply_sequence_command(PG_FUNCTION_ARGS)
 	}
 
 	/* run the CREATE SEQUENCE command */
-	CitusProcessUtility(commandNode, commandString, PROCESS_UTILITY_TOPLEVEL, NULL,
+	CitusProcessUtility(commandNode, commandString, PROCESS_UTILITY_QUERY, NULL,
 						None_Receiver, NULL);
 	CommandCounterIncrement();
 
@@ -594,9 +596,6 @@ worker_append_table_to_shard(PG_FUNCTION_ARGS)
 	char *sourceSchemaName = NULL;
 	char *sourceTableName = NULL;
 
-	Oid savedUserId = InvalidOid;
-	int savedSecurityContext = 0;
-
 	CheckCitusVersion(ERROR);
 
 	/* We extract schema names and table names from qualified names */
@@ -613,10 +612,13 @@ worker_append_table_to_shard(PG_FUNCTION_ARGS)
 	uint64 shardId = ExtractShardIdFromTableName(shardTableName, false);
 	LockShardResource(shardId, AccessExclusiveLock);
 
-	/* copy remote table's data to this node */
+	/*
+	 * Copy into intermediate results directory, which is automatically cleaned on
+	 * error.
+	 */
 	StringInfo localFilePath = makeStringInfo();
-	appendStringInfo(localFilePath, "base/%s/%s" UINT64_FORMAT,
-					 PG_JOB_CACHE_DIR, TABLE_FILE_PREFIX, shardId);
+	appendStringInfo(localFilePath, "%s/worker_append_table_to_shard_" UINT64_FORMAT,
+					 CreateIntermediateResultsDirectory(), shardId);
 
 	char *sourceQualifiedName = quote_qualified_identifier(sourceSchemaName,
 														   sourceTableName);
@@ -641,7 +643,8 @@ worker_append_table_to_shard(PG_FUNCTION_ARGS)
 		appendStringInfo(sourceCopyCommand, COPY_OUT_COMMAND, sourceQualifiedName);
 	}
 
-	bool received = ReceiveRegularFile(sourceNodeName, sourceNodePort, NULL,
+	char *userName = CurrentUserName();
+	bool received = ReceiveRegularFile(sourceNodeName, sourceNodePort, userName,
 									   sourceCopyCommand,
 									   localFilePath);
 	if (!received)
@@ -664,17 +667,36 @@ worker_append_table_to_shard(PG_FUNCTION_ARGS)
 	/* make sure we are allowed to execute the COPY command */
 	CheckCopyPermissions(localCopyCommand);
 
-	/* need superuser to copy from files */
-	GetUserIdAndSecContext(&savedUserId, &savedSecurityContext);
-	SetUserIdAndSecContext(CitusExtensionOwner(), SECURITY_LOCAL_USERID_CHANGE);
+	Relation shardRelation = table_openrv(localCopyCommand->relation, RowExclusiveLock);
 
-	CitusProcessUtility((Node *) localCopyCommand, queryString->data,
-						PROCESS_UTILITY_TOPLEVEL, NULL, None_Receiver, NULL);
+	/* mimic check from copy.c */
+	if (XactReadOnly && !shardRelation->rd_islocaltemp)
+	{
+		PreventCommandIfReadOnly("COPY FROM");
+	}
 
-	SetUserIdAndSecContext(savedUserId, savedSecurityContext);
+	ParseState *parseState = make_parsestate(NULL);
+	(void) addRangeTableEntryForRelation(parseState, shardRelation,
+#if PG_VERSION_NUM >= PG_VERSION_12
+										 RowExclusiveLock,
+#endif
+										 NULL, false, false);
+
+	CopyState copyState = BeginCopyFrom(parseState,
+										shardRelation,
+										localCopyCommand->filename,
+										localCopyCommand->is_program,
+										NULL,
+										localCopyCommand->attlist,
+										localCopyCommand->options);
+	CopyFrom(copyState);
+	EndCopyFrom(copyState);
+
+	free_parsestate(parseState);
 
 	/* finally delete the temporary file we created */
 	CitusDeleteFile(localFilePath->data);
+	table_close(shardRelation, NoLock);
 
 	PG_RETURN_VOID();
 }
@@ -782,7 +804,7 @@ AlterSequenceMinMax(Oid sequenceId, char *schemaName, char *sequenceName,
 
 		/* since the command is an AlterSeqStmt, a dummy command string works fine */
 		CitusProcessUtility((Node *) alterSequenceStatement, dummyString,
-							PROCESS_UTILITY_TOPLEVEL, NULL, None_Receiver, NULL);
+							PROCESS_UTILITY_QUERY, NULL, None_Receiver, NULL);
 	}
 }
 

src/backend/distributed/worker/worker_merge_protocol.c

@@ -37,6 +37,7 @@
 
 #include "executor/spi.h"
 #include "nodes/makefuncs.h"
+#include "parser/parse_relation.h"
 #include "parser/parse_type.h"
 #include "storage/lmgr.h"
 #include "utils/acl.h"
@@ -183,8 +184,6 @@ worker_merge_files_into_table(PG_FUNCTION_ARGS)
 	StringInfo jobSchemaName = JobSchemaName(jobId);
 	StringInfo taskTableName = TaskTableName(taskId);
 	StringInfo taskDirectoryName = TaskDirectoryName(jobId, taskId);
-	Oid savedUserId = InvalidOid;
-	int savedSecurityContext = 0;
 	Oid userId = GetUserId();
 
 	/* we should have the same number of column names and types */
@@ -233,14 +232,9 @@ worker_merge_files_into_table(PG_FUNCTION_ARGS)
 
 	CreateTaskTable(jobSchemaName, taskTableName, columnNameList, columnTypeList);
 
-	/* need superuser to copy from files */
-	GetUserIdAndSecContext(&savedUserId, &savedSecurityContext);
-	SetUserIdAndSecContext(CitusExtensionOwner(), SECURITY_LOCAL_USERID_CHANGE);
-
 	CopyTaskFilesFromDirectory(jobSchemaName, taskTableName, taskDirectoryName,
 							   userId);
 
-	SetUserIdAndSecContext(savedUserId, savedSecurityContext);
 	PG_RETURN_VOID();
 }
 
@@ -569,8 +563,8 @@ CopyTaskFilesFromDirectory(StringInfo schemaName, StringInfo relationName,
 		appendStringInfo(fullFilename, "%s/%s", directoryName, baseFilename);
 
 		/* build relation object and copy statement */
-		RangeVar *relation = makeRangeVar(schemaName->data, relationName->data, -1);
-		CopyStmt *copyStatement = CopyStatement(relation, fullFilename->data);
+		RangeVar *rangeVar = makeRangeVar(schemaName->data, relationName->data, -1);
+		CopyStmt *copyStatement = CopyStatement(rangeVar, fullFilename->data);
 		if (BinaryWorkerCopyFormat)
 		{
 			DefElem *copyOption = makeDefElem("format", (Node *) makeString("binary"),
@@ -579,12 +573,28 @@ CopyTaskFilesFromDirectory(StringInfo schemaName, StringInfo relationName,
 		}
 
 		{
-			ParseState *pstate = make_parsestate(NULL);
-			pstate->p_sourcetext = queryString;
+			ParseState *parseState = make_parsestate(NULL);
+			parseState->p_sourcetext = queryString;
 
-			DoCopy(pstate, copyStatement, -1, -1, &copiedRowCount);
+			Relation relation = table_openrv(rangeVar, RowExclusiveLock);
+			(void) addRangeTableEntryForRelation(parseState, relation,
+#if PG_VERSION_NUM >= PG_VERSION_12
+												 RowExclusiveLock,
+#endif
+												 NULL, false, false);
 
-			free_parsestate(pstate);
+			CopyState copyState = BeginCopyFrom(parseState,
+												relation,
+												copyStatement->filename,
+												copyStatement->is_program,
+												NULL,
+												copyStatement->attlist,
+												copyStatement->options);
+			copiedRowCount = CopyFrom(copyState);
+			EndCopyFrom(copyState);
+
+			free_parsestate(parseState);
+			table_close(relation, NoLock);
 		}
 
 		copiedRowTotal += copiedRowCount;

src/include/distributed/citus_custom_scan.h

@@ -20,6 +20,7 @@ typedef struct CitusScanState
 	CustomScanState customScanState;  /* underlying custom scan node */
 
 	/* function that gets called before postgres starts its execution */
+	bool finishedPreScan;          /* flag to check if the pre scan is finished */
 	void (*PreExecScan)(struct CitusScanState *scanState);
 
 	DistributedPlan *distributedPlan; /* distributed execution plan */

src/include/distributed/commands.h

@@ -64,6 +64,26 @@ typedef enum ExtractForeignKeyConstraintsMode
 	EXCLUDE_SELF_REFERENCES = 1 << 2
 } ExtractForeignKeyConstraintMode;
 
+
+/*
+ * Flags that can be passed to GetForeignKeyIdsForColumn to
+ * indicate whether relationId argument should match:
+ *   - referencing relation or,
+ *   - referenced relation,
+ *  or we are searching for both sides.
+ */
+typedef enum SearchForeignKeyColumnFlags
+{
+	/* relationId argument should match referencing relation */
+	SEARCH_REFERENCING_RELATION = 1 << 0,
+
+	/* relationId argument should match referenced relation */
+	SEARCH_REFERENCED_RELATION = 1 << 1,
+
+	/* callers can also pass union of above flags */
+} SearchForeignKeyColumnFlags;
+
+
 /* cluster.c - forward declarations */
 extern List * PreprocessClusterStmt(Node *node, const char *clusterCommand);
 
@@ -119,15 +139,21 @@ extern void ErrorIfUnsupportedForeignConstraintExists(Relation relation,
 													  Var *distributionColumn,
 													  uint32 colocationId);
 extern void ErrorOutForFKeyBetweenPostgresAndCitusLocalTable(Oid localTableId);
+extern bool ColumnReferencedByAnyForeignKey(char *columnName, Oid relationId);
+extern bool ColumnAppearsInForeignKey(char *columnName, Oid relationId);
 extern bool ColumnAppearsInForeignKeyToReferenceTable(char *columnName, Oid
 													  relationId);
 extern List * GetReferencingForeignConstaintCommands(Oid relationOid);
+extern bool AnyForeignKeyDependsOnIndex(Oid indexId);
 extern bool HasForeignKeyToCitusLocalTable(Oid relationId);
 extern bool HasForeignKeyToReferenceTable(Oid relationOid);
 extern bool TableReferenced(Oid relationOid);
 extern bool TableReferencing(Oid relationOid);
+extern bool ConstraintIsAUniquenessConstraint(char *inputConstaintName, Oid relationId);
 extern bool ConstraintIsAForeignKey(char *inputConstaintName, Oid relationOid);
-extern Oid GetForeignKeyOidByName(char *inputConstaintName, Oid relationId);
+extern bool ConstraintWithNameIsOfType(char *inputConstaintName, Oid relationId,
+									   char targetConstraintType);
+extern bool ConstraintWithIdIsOfType(Oid constraintId, char targetConstraintType);
 extern void ErrorIfTableHasExternalForeignKeys(Oid relationId);
 extern List * GetForeignKeyOids(Oid relationId, int flags);
 extern Oid GetReferencedTableId(Oid foreignKeyId);

src/include/distributed/connection_management.h

@@ -178,6 +178,9 @@ typedef struct ConnectionHashEntry
 {
 	ConnectionHashKey key;
 	dlist_head *connections;
+
+	/* connections list is valid or not */
+	bool isValid;
 } ConnectionHashEntry;
 
 /* hash entry for cached connection parameters */

src/include/distributed/deparse_shard_query.h

@@ -28,7 +28,8 @@ extern void SetTaskQueryString(Task *task, char *queryString);
 extern void SetTaskQueryStringList(Task *task, List *queryStringList);
 extern char * TaskQueryString(Task *task);
 extern char * TaskQueryStringAtIndex(Task *task, int index);
-extern bool UpdateRelationsToLocalShardTables(Node *node, List *relationShardList);
 extern int GetTaskQueryType(Task *task);
+extern void AddInsertAliasIfNeeded(Query *query);
+
 
 #endif /* DEPARSE_SHARD_QUERY_H */

src/include/distributed/distribution_column.h

@@ -19,6 +19,9 @@
 
 
 /* Remaining metadata utility functions  */
+extern Var * FindColumnWithNameOnTargetRelation(Oid sourceRelationId,
+												char *sourceColumnName,
+												Oid targetRelationId);
 extern Var * BuildDistributionKeyFromColumnName(Relation distributedRelation,
 												char *columnName);
 extern char * ColumnToColumnName(Oid relationId, char *columnNodeString);

src/include/distributed/foreign_key_relationship.h

@@ -20,5 +20,8 @@ extern List * ReferencingRelationIdList(Oid relationId);
 extern void SetForeignConstraintRelationshipGraphInvalid(void);
 extern bool IsForeignConstraintRelationshipGraphValid(void);
 extern void ClearForeignConstraintRelationshipGraphContext(void);
+extern HTAB * CreateOidVisitedHashSet(void);
+extern bool OidVisited(HTAB *oidVisitedMap, Oid oid);
+extern void VisitOid(HTAB *oidVisitedMap, Oid oid);
 
 #endif

src/include/distributed/local_executor.h

@@ -48,5 +48,8 @@ extern bool TaskAccessesLocalNode(Task *task);
 extern void ErrorIfTransactionAccessedPlacementsLocally(void);
 extern void DisableLocalExecution(void);
 extern void SetLocalExecutionStatus(LocalExecutionStatus newStatus);
+extern void ExtractParametersForLocalExecution(ParamListInfo paramListInfo,
+											   Oid **parameterTypes,
+											   const char ***parameterValues);
 
 #endif /* LOCAL_EXECUTION_H */

src/include/distributed/local_plan_cache.h

@@ -5,6 +5,7 @@ extern bool IsLocalPlanCachingSupported(Job *currentJob,
 										DistributedPlan *originalDistributedPlan);
 extern PlannedStmt * GetCachedLocalPlan(Task *task, DistributedPlan *distributedPlan);
 extern void CacheLocalPlanForShardQuery(Task *task,
-										DistributedPlan *originalDistributedPlan);
+										DistributedPlan *originalDistributedPlan,
+										ParamListInfo paramListInfo);
 
 #endif /* LOCAL_PLAN_CACHE */

src/include/distributed/maintenanced.h

@@ -25,6 +25,7 @@ extern void StopMaintenanceDaemon(Oid databaseId);
 extern void TriggerMetadataSync(Oid databaseId);
 extern void InitializeMaintenanceDaemon(void);
 extern void InitializeMaintenanceDaemonBackend(void);
+extern bool LockCitusExtension(void);
 
 extern void CitusMaintenanceDaemonMain(Datum main_arg);
 

src/include/distributed/metadata/dependency.h

@@ -15,12 +15,16 @@
 #include "postgres.h"
 
 #include "catalog/objectaddress.h"
+#include "catalog/pg_depend.h"
 #include "nodes/pg_list.h"
 
 extern List * GetUniqueDependenciesList(List *objectAddressesList);
 extern List * GetDependenciesForObject(const ObjectAddress *target);
 extern List * OrderObjectAddressListInDependencyOrder(List *objectAddressList);
 extern bool SupportedDependencyByCitus(const ObjectAddress *address);
+extern List * GetPgDependTuplesForDependingObjects(Oid targetObjectClassId,
+												   Oid targetObjectId);
 extern List * GetDependingViews(Oid relationId);
+extern Oid GetDependingView(Form_pg_depend pg_depend);
 
 #endif /* CITUS_DEPENDENCY_H */

src/include/distributed/metadata_sync.h

@@ -50,11 +50,14 @@ extern char * PlacementUpsertCommand(uint64 shardId, uint64 placementId, int sha
 extern void CreateTableMetadataOnWorkers(Oid relationId);
 extern void MarkNodeHasMetadata(const char *nodeName, int32 nodePort, bool hasMetadata);
 extern void MarkNodeMetadataSynced(const char *nodeName, int32 nodePort, bool synced);
-extern MetadataSyncResult SyncMetadataToNodes(void);
+extern BackgroundWorkerHandle * SpawnSyncMetadataToNodes(Oid database, Oid owner);
 extern bool SendOptionalCommandListToWorkerInTransaction(const char *nodeName, int32
 														 nodePort,
 														 const char *nodeUser,
 														 List *commandList);
+extern void SyncMetadataToNodesMain(Datum main_arg);
+extern void SignalMetadataSyncDaemon(Oid database, int sig);
+extern bool ShouldInitiateMetadataSync(bool *lockFailure);
 
 #define DELETE_ALL_NODES "TRUNCATE pg_dist_node CASCADE"
 #define REMOVE_ALL_CLUSTERED_TABLES_COMMAND \

src/include/distributed/metadata_utility.h

@@ -35,6 +35,8 @@
 #define PG_TOTAL_RELATION_SIZE_FUNCTION "pg_total_relation_size(%s)"
 #define CSTORE_TABLE_SIZE_FUNCTION "cstore_table_size(%s)"
 
+#define UPDATE_SHARD_STATISTICS_COLUMN_COUNT 4
+
 /* In-memory representation of a typed tuple in pg_dist_shard. */
 typedef struct ShardInterval
 {
@@ -169,5 +171,8 @@ extern ShardInterval * DeformedDistShardTupleToShardInterval(Datum *datumArray,
 															 int32 intervalTypeMod);
 extern void GetIntervalTypeInfo(char partitionMethod, Var *partitionColumn,
 								Oid *intervalTypeId, int32 *intervalTypeMod);
+extern List * SendShardStatisticsQueriesInParallel(List *citusTableIds, bool
+												   useDistributedTransaction, bool
+												   useShardMinMaxQuery);
 
 #endif   /* METADATA_UTILITY_H */

src/include/distributed/transaction_management.h

@@ -121,6 +121,7 @@ extern void InitializeTransactionManagement(void);
 /* other functions */
 extern List * ActiveSubXactContexts(void);
 extern StringInfo BeginAndSetDistributedTransactionIdCommand(void);
+extern void TriggerMetadataSyncOnCommit(void);
 
 
 #endif /*  TRANSACTION_MANAGMENT_H */

src/include/distributed/worker_manager.h

@@ -80,7 +80,6 @@ extern WorkerNode * CoordinatorNodeIfAddedAsWorkerOrError(void);
 extern void ErrorIfCoordinatorNotAddedAsWorkerNode(void);
 extern List * DistributedTablePlacementNodeList(LOCKMODE lockMode);
 extern bool NodeCanHaveDistTablePlacements(WorkerNode *node);
-extern uint32 ActiveReadableNonCoordinatorNodeCount(void);
 extern List * ActiveReadableNonCoordinatorNodeList(void);
 extern List * ActiveReadableNodeList(void);
 extern WorkerNode * FindWorkerNode(const char *nodeName, int32 nodePort);

src/include/distributed/worker_protocol.h

@@ -35,7 +35,6 @@
 #define JOB_SCHEMA_PREFIX "pg_merge_job_"
 #define TASK_FILE_PREFIX "task_"
 #define TASK_TABLE_PREFIX "task_"
-#define TABLE_FILE_PREFIX "table_"
 #define PARTITION_FILE_PREFIX "p_"
 #define ATTEMPT_FILE_SUFFIX ".attempt"
 #define MERGE_TABLE_SUFFIX "_merge"

src/test/regress/bin/normalize.sed

@@ -181,3 +181,6 @@ s/wrong data type: [0-9]+, expected [0-9]+/wrong data type: XXXX, expected XXXX/
 
 # Errors with relation OID does not exist
 s/relation with OID [0-9]+ does not exist/relation with OID XXXX does not exist/g
+
+# ignore DEBUG1 messages that Postgres generates
+/^DEBUG:  rehashing catalog cache id [0-9]+$/d

src/test/regress/expected/aggregate_support.out

@@ -712,6 +712,19 @@ select array_agg(val order by valf) from aggdata;
  {0,NULL,2,3,5,2,4,NULL,NULL,8,NULL}
 (1 row)
 
+-- test by using some other node types as arguments to agg
+select key, percentile_cont((key - (key > 4)::int) / 10.0) within group(order by val) from aggdata group by key;
+ key | percentile_cont
+---------------------------------------------------------------------
+   1 |               2
+   2 |             2.4
+   3 |               4
+   5 |
+   6 |
+   7 |               8
+   9 |               0
+(7 rows)
+
 -- Test TransformSubqueryNode
 select * FROM (
     SELECT key, mode() within group (order by floor(agg1.val/2)) m from aggdata agg1
@@ -932,5 +945,100 @@ SELECT square_func(5), a, count(a) FROM t1 GROUP BY a;
 ERROR:  function aggregate_support.square_func(integer) does not exist
 HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
 CONTEXT:  while executing command on localhost:xxxxx
+-- Test the cases where the worker agg exec. returns no tuples.
+CREATE TABLE dist_table (dist_col int, agg_col numeric);
+SELECT create_distributed_table('dist_table', 'dist_col');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+CREATE TABLE ref_table (int_col int);
+SELECT create_reference_table('ref_table');
+ create_reference_table
+---------------------------------------------------------------------
+
+(1 row)
+
+SELECT PERCENTILE_DISC(.25) WITHIN GROUP (ORDER BY agg_col)
+FROM dist_table
+LEFT JOIN ref_table ON TRUE;
+ percentile_disc
+---------------------------------------------------------------------
+
+(1 row)
+
+SELECT PERCENTILE_DISC(.25) WITHIN GROUP (ORDER BY agg_col)
+FROM (SELECT *, random() FROM dist_table) a;
+ percentile_disc
+---------------------------------------------------------------------
+
+(1 row)
+
+SELECT PERCENTILE_DISC((2 > random())::int::numeric / 10) WITHIN GROUP (ORDER BY agg_col)
+FROM dist_table
+LEFT JOIN ref_table ON TRUE;
+ percentile_disc
+---------------------------------------------------------------------
+
+(1 row)
+
+SELECT SUM(COALESCE(agg_col, 3))
+FROM dist_table
+LEFT JOIN ref_table ON TRUE;
+ sum
+---------------------------------------------------------------------
+
+(1 row)
+
+SELECT AVG(COALESCE(agg_col, 10))
+FROM dist_table
+LEFT JOIN ref_table ON TRUE;
+ avg
+---------------------------------------------------------------------
+
+(1 row)
+
+insert into dist_table values (2, 11.2), (3, NULL), (6, 3.22), (3, 4.23), (5, 5.25), (4, 63.4), (75, NULL), (80, NULL), (96, NULL), (8, 1078), (0, 1.19);
+-- run the same queries after loading some data
+SELECT PERCENTILE_DISC(.25) WITHIN GROUP (ORDER BY agg_col)
+FROM dist_table
+LEFT JOIN ref_table ON TRUE;
+ percentile_disc
+---------------------------------------------------------------------
+            3.22
+(1 row)
+
+SELECT PERCENTILE_DISC(.25) WITHIN GROUP (ORDER BY agg_col)
+FROM (SELECT *, random() FROM dist_table) a;
+ percentile_disc
+---------------------------------------------------------------------
+            3.22
+(1 row)
+
+SELECT PERCENTILE_DISC((2 > random())::int::numeric / 10) WITHIN GROUP (ORDER BY agg_col)
+FROM dist_table
+LEFT JOIN ref_table ON TRUE;
+ percentile_disc
+---------------------------------------------------------------------
+            1.19
+(1 row)
+
+SELECT floor(SUM(COALESCE(agg_col, 3)))
+FROM dist_table
+LEFT JOIN ref_table ON TRUE;
+ floor
+---------------------------------------------------------------------
+  1178
+(1 row)
+
+SELECT floor(AVG(COALESCE(agg_col, 10)))
+FROM dist_table
+LEFT JOIN ref_table ON TRUE;
+ floor
+---------------------------------------------------------------------
+   109
+(1 row)
+
 set client_min_messages to error;
 drop schema aggregate_support cascade;

src/test/regress/expected/coordinator_shouldhaveshards.out

@@ -500,6 +500,102 @@ NOTICE:  executing the command locally: SELECT count(*) AS count FROM (coordinat
 (1 row)
 
 ROLLBACK;
+-- issue 4508 table_1 and table_2 are used to test
+-- some edge cases around intermediate result pruning
+CREATE TABLE table_1 (key int, value text);
+SELECT create_distributed_table('table_1', 'key');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+CREATE TABLE table_2 (key int, value text);
+SELECT create_distributed_table('table_2', 'key');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+INSERT INTO table_1    VALUES (1, '1'), (2, '2'), (3, '3'), (4, '4');
+INSERT INTO table_2    VALUES (1, '1'), (2, '2'), (3, '3'), (4, '4'), (5, '5'), (6, '6');
+SET citus.log_intermediate_results TO ON;
+SET client_min_messages to debug1;
+WITH a AS (SELECT * FROM table_1 ORDER BY 1,2 DESC LIMIT 1)
+SELECT count(*),
+key
+FROM a JOIN table_2 USING (key)
+GROUP BY key
+HAVING (max(table_2.value) >= (SELECT value FROM a));
+DEBUG:  generating subplan XXX_1 for CTE a: SELECT key, value FROM coordinator_shouldhaveshards.table_1 ORDER BY key, value DESC LIMIT 1
+DEBUG:  push down of limit count: 1
+DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT count(*) AS count, a.key FROM ((SELECT intermediate_result.key, intermediate_result.value FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(key integer, value text)) a JOIN coordinator_shouldhaveshards.table_2 USING (key)) GROUP BY a.key HAVING (max(table_2.value) OPERATOR(pg_catalog.>=) (SELECT a_1.value FROM (SELECT intermediate_result.key, intermediate_result.value FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(key integer, value text)) a_1))
+DEBUG:  Subplan XXX_1 will be written to local file
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+NOTICE:  executing the command locally: SELECT key, value FROM coordinator_shouldhaveshards.table_1_1503036 table_1 WHERE true ORDER BY key, value DESC LIMIT '1'::bigint
+NOTICE:  executing the command locally: SELECT key, value FROM coordinator_shouldhaveshards.table_1_1503039 table_1 WHERE true ORDER BY key, value DESC LIMIT '1'::bigint
+NOTICE:  executing the command locally: SELECT count(*) AS count, worker_column_1 AS key, max(worker_column_2) AS worker_column_3 FROM (SELECT a.key AS worker_column_1, table_2.value AS worker_column_2 FROM ((SELECT intermediate_result.key, intermediate_result.value FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(key integer, value text)) a JOIN coordinator_shouldhaveshards.table_2_1503042 table_2(key, value) USING (key))) worker_subquery GROUP BY worker_column_1
+NOTICE:  executing the command locally: SELECT count(*) AS count, worker_column_1 AS key, max(worker_column_2) AS worker_column_3 FROM (SELECT a.key AS worker_column_1, table_2.value AS worker_column_2 FROM ((SELECT intermediate_result.key, intermediate_result.value FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(key integer, value text)) a JOIN coordinator_shouldhaveshards.table_2_1503045 table_2(key, value) USING (key))) worker_subquery GROUP BY worker_column_1
+ count | key
+---------------------------------------------------------------------
+     1 |   1
+(1 row)
+
+WITH a AS (SELECT * FROM table_1 ORDER BY 1,2 DESC LIMIT 1)
+INSERT INTO table_1 SELECT count(*),
+key
+FROM a JOIN table_2 USING (key)
+GROUP BY key
+HAVING (max(table_2.value) >= (SELECT value FROM a));
+DEBUG:  Group by list without distribution column is not allowed  in distributed INSERT ... SELECT queries
+DEBUG:  generating subplan XXX_1 for CTE a: SELECT key, value FROM coordinator_shouldhaveshards.table_1 ORDER BY key, value DESC LIMIT 1
+DEBUG:  push down of limit count: 1
+DEBUG:  generating subplan XXX_2 for subquery SELECT count(*) AS count, a.key FROM ((SELECT intermediate_result.key, intermediate_result.value FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(key integer, value text)) a JOIN coordinator_shouldhaveshards.table_2 USING (key)) GROUP BY a.key HAVING (max(table_2.value) OPERATOR(pg_catalog.>=) (SELECT a_1.value FROM (SELECT intermediate_result.key, intermediate_result.value FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(key integer, value text)) a_1))
+DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT int4(count) AS key, (key)::text AS value FROM (SELECT intermediate_result.count, intermediate_result.key FROM read_intermediate_result('XXX_2'::text, 'binary'::citus_copy_format) intermediate_result(count bigint, key integer)) citus_insert_select_subquery
+DEBUG:  Collecting INSERT ... SELECT results on coordinator
+DEBUG:  Subplan XXX_1 will be written to local file
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+NOTICE:  executing the command locally: SELECT key, value FROM coordinator_shouldhaveshards.table_1_1503036 table_1 WHERE true ORDER BY key, value DESC LIMIT '1'::bigint
+NOTICE:  executing the command locally: SELECT key, value FROM coordinator_shouldhaveshards.table_1_1503039 table_1 WHERE true ORDER BY key, value DESC LIMIT '1'::bigint
+DEBUG:  Subplan XXX_2 will be written to local file
+NOTICE:  executing the command locally: SELECT count(*) AS count, worker_column_1 AS key, max(worker_column_2) AS worker_column_3 FROM (SELECT a.key AS worker_column_1, table_2.value AS worker_column_2 FROM ((SELECT intermediate_result.key, intermediate_result.value FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(key integer, value text)) a JOIN coordinator_shouldhaveshards.table_2_1503042 table_2(key, value) USING (key))) worker_subquery GROUP BY worker_column_1
+NOTICE:  executing the command locally: SELECT count(*) AS count, worker_column_1 AS key, max(worker_column_2) AS worker_column_3 FROM (SELECT a.key AS worker_column_1, table_2.value AS worker_column_2 FROM ((SELECT intermediate_result.key, intermediate_result.value FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(key integer, value text)) a JOIN coordinator_shouldhaveshards.table_2_1503045 table_2(key, value) USING (key))) worker_subquery GROUP BY worker_column_1
+NOTICE:  executing the command locally: SELECT int4(count) AS key, (key)::text AS value FROM (SELECT intermediate_result.count, intermediate_result.key FROM read_intermediate_result('XXX_2'::text, 'binary'::citus_copy_format) intermediate_result(count bigint, key integer)) citus_insert_select_subquery
+NOTICE:  executing the copy locally for shard xxxxx
+WITH stats AS (
+  SELECT count(key) m FROM table_1
+),
+inserts AS (
+  INSERT INTO table_2
+  SELECT key, count(*)
+  FROM table_1
+  WHERE key >= (SELECT m FROM stats)
+  GROUP BY key
+  HAVING count(*) <= (SELECT m FROM stats)
+  LIMIT 1
+  RETURNING *
+) SELECT count(*) FROM inserts;
+DEBUG:  generating subplan XXX_1 for CTE stats: SELECT count(key) AS m FROM coordinator_shouldhaveshards.table_1
+DEBUG:  generating subplan XXX_2 for CTE inserts: INSERT INTO coordinator_shouldhaveshards.table_2 (key, value) SELECT key, count(*) AS count FROM coordinator_shouldhaveshards.table_1 WHERE (key OPERATOR(pg_catalog.>=) (SELECT stats.m FROM (SELECT intermediate_result.m FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(m bigint)) stats)) GROUP BY key HAVING (count(*) OPERATOR(pg_catalog.<=) (SELECT stats.m FROM (SELECT intermediate_result.m FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(m bigint)) stats)) LIMIT 1 RETURNING table_2.key, table_2.value
+DEBUG:  LIMIT clauses are not allowed in distributed INSERT ... SELECT queries
+DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT count(*) AS count FROM (SELECT intermediate_result.key, intermediate_result.value FROM read_intermediate_result('XXX_2'::text, 'binary'::citus_copy_format) intermediate_result(key integer, value text)) inserts
+DEBUG:  Subplan XXX_1 will be written to local file
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+NOTICE:  executing the command locally: SELECT count(key) AS m FROM coordinator_shouldhaveshards.table_1_1503036 table_1 WHERE true
+NOTICE:  executing the command locally: SELECT count(key) AS m FROM coordinator_shouldhaveshards.table_1_1503039 table_1 WHERE true
+DEBUG:  Subplan XXX_2 will be written to local file
+DEBUG:  Collecting INSERT ... SELECT results on coordinator
+NOTICE:  executing the command locally: SELECT worker_column_1 AS key, count(*) AS value, count(*) AS worker_column_3 FROM (SELECT table_1.key AS worker_column_1 FROM coordinator_shouldhaveshards.table_1_1503036 table_1 WHERE (table_1.key OPERATOR(pg_catalog.>=) (SELECT stats.m FROM (SELECT intermediate_result.m FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(m bigint)) stats))) worker_subquery GROUP BY worker_column_1
+NOTICE:  executing the command locally: SELECT worker_column_1 AS key, count(*) AS value, count(*) AS worker_column_3 FROM (SELECT table_1.key AS worker_column_1 FROM coordinator_shouldhaveshards.table_1_1503039 table_1 WHERE (table_1.key OPERATOR(pg_catalog.>=) (SELECT stats.m FROM (SELECT intermediate_result.m FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(m bigint)) stats))) worker_subquery GROUP BY worker_column_1
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM (SELECT intermediate_result.key, intermediate_result.value FROM read_intermediate_result('XXX_2'::text, 'binary'::citus_copy_format) intermediate_result(key integer, value text)) inserts
+ count
+---------------------------------------------------------------------
+     0
+(1 row)
+
+RESET client_min_messages;
 \set VERBOSITY terse
 DROP TABLE ref_table;
 NOTICE:  executing the command locally: DROP TABLE IF EXISTS coordinator_shouldhaveshards.ref_table_xxxxx CASCADE
@@ -509,7 +605,7 @@ DROP TABLE dist_table;
 DROP TABLE ref;
 NOTICE:  executing the command locally: DROP TABLE IF EXISTS coordinator_shouldhaveshards.ref_xxxxx CASCADE
 DROP SCHEMA coordinator_shouldhaveshards CASCADE;
-NOTICE:  drop cascades to table local
+NOTICE:  drop cascades to 7 other objects
 SELECT 1 FROM master_set_node_property('localhost', :master_port, 'shouldhaveshards', false);
  ?column?
 ---------------------------------------------------------------------

src/test/regress/expected/cursors.out

@@ -0,0 +1,218 @@
+CREATE SCHEMA cursors;
+SET search_path TO cursors;
+CREATE TABLE distributed_table (key int, value text);
+SELECT create_distributed_table('distributed_table', 'key');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- load some data, but not very small amounts because RETURN QUERY in plpgsql
+-- hard codes the cursor fetch to 50 rows on PG 12, though they might increase
+-- it sometime in the future, so be mindful
+INSERT INTO distributed_table SELECT i  % 10, i::text FROM  generate_series(0, 1000) i;
+CREATE OR REPLACE FUNCTION simple_cursor_on_dist_table(cursor_name refcursor) RETURNS refcursor AS '
+BEGIN
+    OPEN $1 FOR SELECT DISTINCT key FROM distributed_table ORDER BY 1;
+    RETURN $1;
+END;
+' LANGUAGE plpgsql;
+CREATE OR REPLACE FUNCTION cursor_with_intermediate_result_on_dist_table(cursor_name refcursor) RETURNS refcursor AS '
+BEGIN
+    OPEN $1 FOR
+		WITH cte_1 AS (SELECT * FROM distributed_table OFFSET 0)
+			SELECT DISTINCT key FROM distributed_table WHERE value in (SELECT value FROM cte_1) ORDER BY 1;
+    RETURN $1;
+END;
+' LANGUAGE plpgsql;
+CREATE OR REPLACE FUNCTION cursor_with_intermediate_result_on_dist_table_with_param(cursor_name refcursor, filter text) RETURNS refcursor AS '
+BEGIN
+    OPEN $1 FOR
+		WITH cte_1 AS (SELECT * FROM distributed_table WHERE value < $2 OFFSET 0)
+			SELECT DISTINCT key FROM distributed_table WHERE value in (SELECT value FROM cte_1) ORDER BY 1;
+    RETURN $1;
+END;
+' LANGUAGE plpgsql;
+-- pretty basic query with cursors
+-- Citus should plan/execute once and pull
+-- the results to coordinator, then serve it
+-- from the coordinator
+BEGIN;
+	SELECT simple_cursor_on_dist_table('cursor_1');
+ simple_cursor_on_dist_table
+---------------------------------------------------------------------
+ cursor_1
+(1 row)
+
+	SET LOCAL citus.log_intermediate_results TO ON;
+	SET LOCAL client_min_messages TO DEBUG1;
+	FETCH 5 IN cursor_1;
+ key
+---------------------------------------------------------------------
+   0
+   1
+   2
+   3
+   4
+(5 rows)
+
+	FETCH 50 IN cursor_1;
+ key
+---------------------------------------------------------------------
+   5
+   6
+   7
+   8
+   9
+(5 rows)
+
+	FETCH ALL IN cursor_1;
+ key
+---------------------------------------------------------------------
+(0 rows)
+
+COMMIT;
+BEGIN;
+	SELECT cursor_with_intermediate_result_on_dist_table('cursor_1');
+ cursor_with_intermediate_result_on_dist_table
+---------------------------------------------------------------------
+ cursor_1
+(1 row)
+
+	-- multiple FETCH commands should not trigger re-running the subplans
+	SET LOCAL citus.log_intermediate_results TO ON;
+	SET LOCAL client_min_messages TO DEBUG1;
+	FETCH 5 IN cursor_1;
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+ key
+---------------------------------------------------------------------
+   0
+   1
+   2
+   3
+   4
+(5 rows)
+
+	FETCH 1 IN cursor_1;
+ key
+---------------------------------------------------------------------
+   5
+(1 row)
+
+	FETCH ALL IN cursor_1;
+ key
+---------------------------------------------------------------------
+   6
+   7
+   8
+   9
+(4 rows)
+
+	FETCH 5 IN cursor_1;
+ key
+---------------------------------------------------------------------
+(0 rows)
+
+COMMIT;
+BEGIN;
+	SELECT cursor_with_intermediate_result_on_dist_table_with_param('cursor_1', '600');
+ cursor_with_intermediate_result_on_dist_table_with_param
+---------------------------------------------------------------------
+ cursor_1
+(1 row)
+
+	-- multiple FETCH commands should not trigger re-running the subplans
+	-- also test with parameters
+	SET LOCAL citus.log_intermediate_results TO ON;
+	SET LOCAL client_min_messages TO DEBUG1;
+	FETCH 1 IN cursor_1;
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+ key
+---------------------------------------------------------------------
+   0
+(1 row)
+
+	FETCH 1 IN cursor_1;
+ key
+---------------------------------------------------------------------
+   1
+(1 row)
+
+	FETCH 1 IN cursor_1;
+ key
+---------------------------------------------------------------------
+   2
+(1 row)
+
+	FETCH 1 IN cursor_1;
+ key
+---------------------------------------------------------------------
+   3
+(1 row)
+
+	FETCH 1 IN cursor_1;
+ key
+---------------------------------------------------------------------
+   4
+(1 row)
+
+	FETCH 1 IN cursor_1;
+ key
+---------------------------------------------------------------------
+   5
+(1 row)
+
+	FETCH ALL IN cursor_1;
+ key
+---------------------------------------------------------------------
+   6
+   7
+   8
+   9
+(4 rows)
+
+COMMIT;
+ CREATE OR REPLACE FUNCTION value_counter() RETURNS TABLE(counter text) LANGUAGE PLPGSQL AS $function$
+ BEGIN
+         return query
+WITH cte AS
+  (SELECT dt.value
+   FROM distributed_table dt
+   WHERE dt.value in
+       (SELECT value
+        FROM distributed_table p
+        GROUP BY p.value
+        HAVING count(*) > 0))
+
+ SELECT * FROM cte;
+END;
+$function$ ;
+SET citus.log_intermediate_results TO ON;
+SET client_min_messages TO DEBUG1;
+\set VERBOSITY terse
+SELECT count(*) from (SELECT value_counter())  as foo;
+DEBUG:  CTE cte is going to be inlined via distributed planning
+DEBUG:  generating subplan XXX_1 for subquery SELECT value FROM cursors.distributed_table p GROUP BY value HAVING (count(*) OPERATOR(pg_catalog.>) 0)
+DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT value FROM (SELECT dt.value FROM cursors.distributed_table dt WHERE (dt.value OPERATOR(pg_catalog.=) ANY (SELECT intermediate_result.value FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(value text)))) cte
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+ count
+---------------------------------------------------------------------
+  1001
+(1 row)
+
+BEGIN;
+	SELECT count(*) from (SELECT value_counter())  as foo;
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+ count
+---------------------------------------------------------------------
+  1001
+(1 row)
+
+COMMIT;
+-- suppress NOTICEs
+SET client_min_messages TO ERROR;
+DROP SCHEMA cursors CASCADE;

src/test/regress/expected/drop_column_partitioned_table.out

@@ -0,0 +1,366 @@
+CREATE SCHEMA drop_column_partitioned_table;
+SET search_path TO drop_column_partitioned_table;
+SET citus.shard_replication_factor TO 1;
+SET citus.next_shard_id TO 2580000;
+-- create a partitioned table with some columns that
+-- are going to be dropped within the tests
+CREATE TABLE sensors(
+col_to_drop_0 text,
+col_to_drop_1 text,
+col_to_drop_2 date,
+col_to_drop_3 inet,
+col_to_drop_4 date,
+measureid integer,
+eventdatetime date,
+measure_data jsonb)
+PARTITION BY RANGE(eventdatetime);
+-- drop column even before attaching any partitions
+ALTER TABLE sensors DROP COLUMN col_to_drop_1;
+-- now attach the first partition and create the distributed table
+CREATE TABLE sensors_2000 PARTITION OF sensors FOR VALUES FROM ('2000-01-01') TO ('2001-01-01');
+SELECT create_distributed_table('sensors', 'measureid');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- prepared statements should work fine even after columns are dropped
+PREPARE drop_col_prepare_insert(int, date, jsonb) AS INSERT INTO sensors (measureid, eventdatetime, measure_data) VALUES ($1, $2, $3);
+PREPARE drop_col_prepare_select(int, date) AS SELECT count(*) FROM sensors WHERE measureid = $1 AND eventdatetime = $2;
+-- execute 7 times to make sure it is cached
+EXECUTE drop_col_prepare_insert(1, '2000-10-01', row_to_json(row(1)));
+EXECUTE drop_col_prepare_insert(1, '2000-10-02', row_to_json(row(1)));
+EXECUTE drop_col_prepare_insert(1, '2000-10-03', row_to_json(row(1)));
+EXECUTE drop_col_prepare_insert(1, '2000-10-04', row_to_json(row(1)));
+EXECUTE drop_col_prepare_insert(1, '2000-10-05', row_to_json(row(1)));
+EXECUTE drop_col_prepare_insert(1, '2000-10-06', row_to_json(row(1)));
+EXECUTE drop_col_prepare_insert(1, '2000-10-07', row_to_json(row(1)));
+EXECUTE drop_col_prepare_select(1, '2000-10-01');
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+EXECUTE drop_col_prepare_select(1, '2000-10-02');
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+EXECUTE drop_col_prepare_select(1, '2000-10-03');
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+EXECUTE drop_col_prepare_select(1, '2000-10-04');
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+EXECUTE drop_col_prepare_select(1, '2000-10-05');
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+EXECUTE drop_col_prepare_select(1, '2000-10-06');
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+EXECUTE drop_col_prepare_select(1, '2000-10-07');
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+-- drop another column before attaching another partition
+-- with .. PARTITION OF .. syntax
+ALTER TABLE sensors DROP COLUMN col_to_drop_0;
+CREATE TABLE sensors_2001 PARTITION OF sensors FOR VALUES FROM ('2001-01-01') TO ('2002-01-01');
+-- drop another column before attaching another partition
+-- with ALTER TABLE .. ATTACH PARTITION
+ALTER TABLE sensors DROP COLUMN col_to_drop_2;
+CREATE TABLE sensors_2002(
+col_to_drop_4 date, col_to_drop_3 inet, measureid integer, eventdatetime date, measure_data jsonb,
+PRIMARY KEY (measureid, eventdatetime, measure_data));
+ALTER TABLE sensors ATTACH PARTITION sensors_2002 FOR VALUES FROM ('2002-01-01') TO ('2003-01-01');
+-- drop another column before attaching another partition
+-- that is already distributed
+ALTER TABLE sensors DROP COLUMN col_to_drop_3;
+CREATE TABLE sensors_2003(
+col_to_drop_4 date, measureid integer, eventdatetime date, measure_data jsonb,
+PRIMARY KEY (measureid, eventdatetime, measure_data));
+SELECT create_distributed_table('sensors_2003', 'measureid');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+ALTER TABLE sensors ATTACH PARTITION sensors_2003 FOR VALUES FROM ('2003-01-01') TO ('2004-01-01');
+CREATE TABLE sensors_2004(
+col_to_drop_4 date, measureid integer NOT NULL, eventdatetime date NOT NULL, measure_data jsonb NOT NULL);
+ALTER TABLE sensors ATTACH PARTITION sensors_2004 FOR VALUES FROM ('2004-01-01') TO ('2005-01-01');
+ALTER TABLE sensors DROP COLUMN col_to_drop_4;
+-- show that all partitions have the same distribution key
+SELECT
+	p.logicalrelid::regclass, column_to_column_name(p.logicalrelid, p.partkey)
+FROM
+	pg_dist_partition p
+WHERE
+	logicalrelid IN ('sensors'::regclass, 'sensors_2000'::regclass,
+					 'sensors_2001'::regclass, 'sensors_2002'::regclass,
+					 'sensors_2003'::regclass, 'sensors_2004'::regclass);
+ logicalrelid | column_to_column_name
+---------------------------------------------------------------------
+ sensors      | measureid
+ sensors_2000 | measureid
+ sensors_2001 | measureid
+ sensors_2002 | measureid
+ sensors_2003 | measureid
+ sensors_2004 | measureid
+(6 rows)
+
+-- show that all the tables prune to the same shard for the same distribution key
+WITH
+	sensors_shardid AS (SELECT * FROM get_shard_id_for_distribution_column('sensors', 3)),
+	sensors_2000_shardid AS (SELECT * FROM get_shard_id_for_distribution_column('sensors_2000', 3)),
+	sensors_2001_shardid AS (SELECT * FROM get_shard_id_for_distribution_column('sensors_2001', 3)),
+	sensors_2002_shardid AS (SELECT * FROM get_shard_id_for_distribution_column('sensors_2002', 3)),
+	sensors_2003_shardid AS (SELECT * FROM get_shard_id_for_distribution_column('sensors_2003', 3)),
+	sensors_2004_shardid AS (SELECT * FROM get_shard_id_for_distribution_column('sensors_2004', 3)),
+	all_shardids AS (SELECT * FROM sensors_shardid UNION SELECT * FROM sensors_2000_shardid UNION
+					 SELECT * FROM sensors_2001_shardid UNION SELECT * FROM sensors_2002_shardid
+					 UNION SELECT * FROM sensors_2003_shardid UNION SELECT * FROM sensors_2004_shardid)
+SELECT logicalrelid, shardid, shardminvalue, shardmaxvalue FROM pg_dist_shard WHERE shardid IN (SELECT * FROM all_shardids);
+ logicalrelid | shardid | shardminvalue | shardmaxvalue
+---------------------------------------------------------------------
+ sensors      | 2580001 | -1073741824   | -1
+ sensors_2000 | 2580005 | -1073741824   | -1
+ sensors_2001 | 2580009 | -1073741824   | -1
+ sensors_2002 | 2580013 | -1073741824   | -1
+ sensors_2003 | 2580017 | -1073741824   | -1
+ sensors_2004 | 2580021 | -1073741824   | -1
+(6 rows)
+
+VACUUM ANALYZE sensors, sensors_2000, sensors_2001, sensors_2002, sensors_2003;
+-- show that both INSERT and SELECT can route to a single node when distribution
+-- key is provided in the query
+EXPLAIN (COSTS FALSE) INSERT INTO sensors VALUES (3, '2000-02-02', row_to_json(row(1)));
+                        QUERY PLAN
+---------------------------------------------------------------------
+ Custom Scan (Citus Adaptive)
+   Task Count: 1
+   Tasks Shown: All
+   ->  Task
+         Node: host=localhost port=xxxxx dbname=regression
+         ->  Insert on sensors_2580001
+               ->  Result
+(7 rows)
+
+EXPLAIN (COSTS FALSE) INSERT INTO sensors_2000 VALUES (3, '2000-01-01', row_to_json(row(1)));
+                        QUERY PLAN
+---------------------------------------------------------------------
+ Custom Scan (Citus Adaptive)
+   Task Count: 1
+   Tasks Shown: All
+   ->  Task
+         Node: host=localhost port=xxxxx dbname=regression
+         ->  Insert on sensors_2000_2580005
+               ->  Result
+(7 rows)
+
+EXPLAIN (COSTS FALSE) INSERT INTO sensors_2001 VALUES (3, '2001-01-01', row_to_json(row(1)));
+                        QUERY PLAN
+---------------------------------------------------------------------
+ Custom Scan (Citus Adaptive)
+   Task Count: 1
+   Tasks Shown: All
+   ->  Task
+         Node: host=localhost port=xxxxx dbname=regression
+         ->  Insert on sensors_2001_2580009
+               ->  Result
+(7 rows)
+
+EXPLAIN (COSTS FALSE) INSERT INTO sensors_2002 VALUES (3, '2002-01-01', row_to_json(row(1)));
+                        QUERY PLAN
+---------------------------------------------------------------------
+ Custom Scan (Citus Adaptive)
+   Task Count: 1
+   Tasks Shown: All
+   ->  Task
+         Node: host=localhost port=xxxxx dbname=regression
+         ->  Insert on sensors_2002_2580013
+               ->  Result
+(7 rows)
+
+EXPLAIN (COSTS FALSE) INSERT INTO sensors_2003 VALUES (3, '2003-01-01', row_to_json(row(1)));
+                        QUERY PLAN
+---------------------------------------------------------------------
+ Custom Scan (Citus Adaptive)
+   Task Count: 1
+   Tasks Shown: All
+   ->  Task
+         Node: host=localhost port=xxxxx dbname=regression
+         ->  Insert on sensors_2003_2580017
+               ->  Result
+(7 rows)
+
+EXPLAIN (COSTS FALSE) SELECT count(*) FROM sensors_2000 WHERE measureid = 3;
+                           QUERY PLAN
+---------------------------------------------------------------------
+ Custom Scan (Citus Adaptive)
+   Task Count: 1
+   Tasks Shown: All
+   ->  Task
+         Node: host=localhost port=xxxxx dbname=regression
+         ->  Aggregate
+               ->  Seq Scan on sensors_2000_2580005 sensors_2000
+                     Filter: (measureid = 3)
+(8 rows)
+
+EXPLAIN (COSTS FALSE) SELECT count(*) FROM sensors_2001 WHERE measureid = 3;
+                           QUERY PLAN
+---------------------------------------------------------------------
+ Custom Scan (Citus Adaptive)
+   Task Count: 1
+   Tasks Shown: All
+   ->  Task
+         Node: host=localhost port=xxxxx dbname=regression
+         ->  Aggregate
+               ->  Seq Scan on sensors_2001_2580009 sensors_2001
+                     Filter: (measureid = 3)
+(8 rows)
+
+EXPLAIN (COSTS FALSE) SELECT count(*) FROM sensors_2002 WHERE measureid = 3;
+                               QUERY PLAN
+---------------------------------------------------------------------
+ Custom Scan (Citus Adaptive)
+   Task Count: 1
+   Tasks Shown: All
+   ->  Task
+         Node: host=localhost port=xxxxx dbname=regression
+         ->  Aggregate
+               ->  Bitmap Heap Scan on sensors_2002_2580013 sensors_2002
+                     Recheck Cond: (measureid = 3)
+                     ->  Bitmap Index Scan on sensors_2002_pkey_2580013
+                           Index Cond: (measureid = 3)
+(10 rows)
+
+EXPLAIN (COSTS FALSE) SELECT count(*) FROM sensors_2003 WHERE measureid = 3;
+                               QUERY PLAN
+---------------------------------------------------------------------
+ Custom Scan (Citus Adaptive)
+   Task Count: 1
+   Tasks Shown: All
+   ->  Task
+         Node: host=localhost port=xxxxx dbname=regression
+         ->  Aggregate
+               ->  Bitmap Heap Scan on sensors_2003_2580017 sensors_2003
+                     Recheck Cond: (measureid = 3)
+                     ->  Bitmap Index Scan on sensors_2003_pkey_2580017
+                           Index Cond: (measureid = 3)
+(10 rows)
+
+-- execute 7 times to make sure it is re-cached
+EXECUTE drop_col_prepare_insert(3, '2000-10-01', row_to_json(row(1)));
+EXECUTE drop_col_prepare_insert(3, '2001-10-01', row_to_json(row(1)));
+EXECUTE drop_col_prepare_insert(3, '2002-10-01', row_to_json(row(1)));
+EXECUTE drop_col_prepare_insert(3, '2003-10-01', row_to_json(row(1)));
+EXECUTE drop_col_prepare_insert(3, '2003-10-02', row_to_json(row(1)));
+EXECUTE drop_col_prepare_insert(4, '2003-10-03', row_to_json(row(1)));
+EXECUTE drop_col_prepare_insert(5, '2003-10-04', row_to_json(row(1)));
+EXECUTE drop_col_prepare_select(3, '2000-10-01');
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+EXECUTE drop_col_prepare_select(3, '2001-10-01');
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+EXECUTE drop_col_prepare_select(3, '2002-10-01');
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+EXECUTE drop_col_prepare_select(3, '2003-10-01');
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+EXECUTE drop_col_prepare_select(3, '2003-10-02');
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+EXECUTE drop_col_prepare_select(4, '2003-10-03');
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+EXECUTE drop_col_prepare_select(5, '2003-10-04');
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+-- non-fast router planner queries should also work
+-- so we switched to DEBUG2 to show that dist. key
+-- and the query is router
+SET client_min_messages TO DEBUG2;
+SELECT count(*) FROM (
+SELECT * FROM sensors WHERE measureid = 3
+	UNION
+SELECT * FROM sensors_2000 WHERE measureid = 3
+	UNION
+SELECT * FROM sensors_2001 WHERE measureid = 3
+	UNION
+SELECT * FROM sensors_2002 WHERE measureid = 3
+	UNION
+SELECT * FROM sensors_2003 WHERE measureid = 3
+	UNION
+SELECT * FROM sensors_2004 WHERE measureid = 3
+) as foo;
+DEBUG:  Creating router plan
+DEBUG:  query has a single distribution column value: 3
+ count
+---------------------------------------------------------------------
+     5
+(1 row)
+
+RESET client_min_messages;
+-- show that all partitions have the same distribution key
+-- even after alter_distributed_table changes the shard count
+-- remove this comment once https://github.com/citusdata/citus/issues/5137 is fixed
+--SELECT alter_distributed_table('sensors', shard_count:='3');
+SELECT
+	p.logicalrelid::regclass, column_to_column_name(p.logicalrelid, p.partkey)
+FROM
+	pg_dist_partition p
+WHERE
+	logicalrelid IN ('sensors'::regclass, 'sensors_2000'::regclass,
+					 'sensors_2001'::regclass, 'sensors_2002'::regclass,
+					 'sensors_2003'::regclass, 'sensors_2004'::regclass);
+ logicalrelid | column_to_column_name
+---------------------------------------------------------------------
+ sensors      | measureid
+ sensors_2000 | measureid
+ sensors_2001 | measureid
+ sensors_2002 | measureid
+ sensors_2003 | measureid
+ sensors_2004 | measureid
+(6 rows)
+
+SET client_min_messages TO WARNING;
+DROP SCHEMA drop_column_partitioned_table CASCADE;

src/test/regress/expected/follower_single_node.out

@@ -233,7 +233,7 @@ SELECT * FROM test WHERE x = 1;
 ERROR:  node group 0 does not have a secondary node
 -- add the the follower as secondary nodes and try again, the SELECT statement
 -- should work this time
-\c - - - :master_port
+\c -reuse-previous=off regression - - :master_port
 SET search_path TO single_node;
 SELECT 1 FROM master_add_node('localhost', :follower_master_port, groupid => 0, noderole => 'secondary');
  ?column?
@@ -350,7 +350,7 @@ SELECT count(*) FROM test WHERE false GROUP BY GROUPING SETS (x,y);
 
 RESET citus.task_assignment_policy;
 -- Cleanup
-\c - - - :master_port
+\c -reuse-previous=off regression - - :master_port
 SET search_path TO single_node;
 SET client_min_messages TO WARNING;
 DROP SCHEMA single_node CASCADE;

src/test/regress/expected/insert_select_repartition.out

@@ -1216,6 +1216,7 @@ ON CONFLICT(c1, c2, c3, c4, c5, c6)
 DO UPDATE SET
  cardinality = enriched.cardinality + excluded.cardinality,
  sum = enriched.sum + excluded.sum;
+DEBUG:  rehashing catalog cache id 14 for pg_opclass; 17 tups, 8 buckets at character 224
 DEBUG:  INSERT target table and the source relation of the SELECT partition column value must be colocated in distributed INSERT ... SELECT
 DEBUG:  Router planner cannot handle multi-shard select queries
 DEBUG:  performing repartitioned INSERT ... SELECT

src/test/regress/expected/isolation_dump_global_wait_edges.out

@@ -28,11 +28,11 @@ step detector-dump-wait-edges:
 
 waiting_transaction_numblocking_transaction_numblocking_transaction_waiting
 
-390            389            f
+395            394            f
 transactionnumberwaitingtransactionnumbers
 
-389
-390            389
+394
+395            394
 step s1-abort:
     ABORT;
 
@@ -75,14 +75,14 @@ step detector-dump-wait-edges:
 
 waiting_transaction_numblocking_transaction_numblocking_transaction_waiting
 
-394            393            f
-395            393            f
-395            394            t
+399            398            f
+400            398            f
+400            399            t
 transactionnumberwaitingtransactionnumbers
 
-393
-394            393
-395            393,394
+398
+399            398
+400            398,399
 step s1-abort:
     ABORT;
 

src/test/regress/expected/isolation_metadata_sync_deadlock.out

@@ -0,0 +1,204 @@
+Parsed test spec with 3 sessions
+
+starting permutation: enable-deadlock-detection reload-conf s2-start-session-level-connection s1-begin s1-update-1 s2-begin-on-worker s2-update-2-on-worker s2-truncate-on-worker s3-invalidate-metadata s3-resync s3-wait s2-update-1-on-worker s1-update-2 s1-commit s2-commit-on-worker disable-deadlock-detection reload-conf s2-stop-connection
+create_distributed_table
+
+
+step enable-deadlock-detection:
+  ALTER SYSTEM SET citus.distributed_deadlock_detection_factor TO 1.1;
+
+step reload-conf:
+    SELECT pg_reload_conf();
+
+pg_reload_conf
+
+t
+step s2-start-session-level-connection:
+ SELECT start_session_level_connection_to_node('localhost', 57638);
+
+start_session_level_connection_to_node
+
+
+step s1-begin:
+  BEGIN;
+
+step s1-update-1:
+  UPDATE deadlock_detection_test SET some_val = 1 WHERE user_id = 1;
+
+step s2-begin-on-worker:
+ SELECT run_commands_on_session_level_connection_to_node('BEGIN');
+
+run_commands_on_session_level_connection_to_node
+
+
+step s2-update-2-on-worker:
+  SELECT run_commands_on_session_level_connection_to_node('UPDATE deadlock_detection_test SET some_val = 2 WHERE user_id = 2');
+
+run_commands_on_session_level_connection_to_node
+
+
+step s2-truncate-on-worker:
+    SELECT run_commands_on_session_level_connection_to_node('TRUNCATE t2');
+
+run_commands_on_session_level_connection_to_node
+
+
+step s3-invalidate-metadata:
+    update pg_dist_node SET metadatasynced = false;
+
+step s3-resync:
+  SELECT trigger_metadata_sync();
+
+trigger_metadata_sync
+
+
+step s3-wait:
+  SELECT pg_sleep(2);
+
+pg_sleep
+
+
+step s2-update-1-on-worker:
+  SELECT run_commands_on_session_level_connection_to_node('UPDATE deadlock_detection_test SET some_val = 2 WHERE user_id = 1');
+ <waiting ...>
+step s1-update-2:
+  UPDATE deadlock_detection_test SET some_val = 1 WHERE user_id = 2;
+ <waiting ...>
+step s1-update-2: <... completed>
+step s2-update-1-on-worker: <... completed>
+run_commands_on_session_level_connection_to_node
+
+
+error in steps s1-update-2 s2-update-1-on-worker: ERROR:  canceling the transaction since it was involved in a distributed deadlock
+step s1-commit:
+  COMMIT;
+
+step s2-commit-on-worker:
+  SELECT run_commands_on_session_level_connection_to_node('COMMIT');
+
+run_commands_on_session_level_connection_to_node
+
+
+step disable-deadlock-detection:
+  ALTER SYSTEM SET citus.distributed_deadlock_detection_factor TO -1;
+
+step reload-conf:
+    SELECT pg_reload_conf();
+
+pg_reload_conf
+
+t
+step s2-stop-connection:
+ SELECT stop_session_level_connection_to_node();
+
+stop_session_level_connection_to_node
+
+
+restore_isolation_tester_func
+
+
+
+starting permutation: increase-retry-interval reload-conf s2-start-session-level-connection s2-begin-on-worker s2-truncate-on-worker s3-invalidate-metadata s3-resync s3-wait s1-count-daemons s1-cancel-metadata-sync s1-count-daemons reset-retry-interval reload-conf s2-commit-on-worker s2-stop-connection s3-resync s3-wait
+create_distributed_table
+
+
+step increase-retry-interval:
+  ALTER SYSTEM SET citus.metadata_sync_retry_interval TO 20000;
+
+step reload-conf:
+    SELECT pg_reload_conf();
+
+pg_reload_conf
+
+t
+step s2-start-session-level-connection:
+ SELECT start_session_level_connection_to_node('localhost', 57638);
+
+start_session_level_connection_to_node
+
+
+step s2-begin-on-worker:
+ SELECT run_commands_on_session_level_connection_to_node('BEGIN');
+
+run_commands_on_session_level_connection_to_node
+
+
+step s2-truncate-on-worker:
+    SELECT run_commands_on_session_level_connection_to_node('TRUNCATE t2');
+
+run_commands_on_session_level_connection_to_node
+
+
+step s3-invalidate-metadata:
+    update pg_dist_node SET metadatasynced = false;
+
+step s3-resync:
+  SELECT trigger_metadata_sync();
+
+trigger_metadata_sync
+
+
+step s3-wait:
+  SELECT pg_sleep(2);
+
+pg_sleep
+
+
+step s1-count-daemons:
+  SELECT count(*) FROM pg_stat_activity WHERE application_name LIKE 'Citus Met%';
+
+count
+
+1
+step s1-cancel-metadata-sync:
+  SELECT pg_cancel_backend(pid) FROM pg_stat_activity WHERE application_name LIKE 'Citus Met%';
+  SELECT pg_sleep(2);
+
+pg_cancel_backend
+
+t
+pg_sleep
+
+
+step s1-count-daemons:
+  SELECT count(*) FROM pg_stat_activity WHERE application_name LIKE 'Citus Met%';
+
+count
+
+0
+step reset-retry-interval:
+  ALTER SYSTEM RESET citus.metadata_sync_retry_interval;
+
+step reload-conf:
+    SELECT pg_reload_conf();
+
+pg_reload_conf
+
+t
+step s2-commit-on-worker:
+  SELECT run_commands_on_session_level_connection_to_node('COMMIT');
+
+run_commands_on_session_level_connection_to_node
+
+
+step s2-stop-connection:
+ SELECT stop_session_level_connection_to_node();
+
+stop_session_level_connection_to_node
+
+
+step s3-resync:
+  SELECT trigger_metadata_sync();
+
+trigger_metadata_sync
+
+
+step s3-wait:
+  SELECT pg_sleep(2);
+
+pg_sleep
+
+
+restore_isolation_tester_func
+
+

src/test/regress/expected/local_shard_copy.out

@@ -3,10 +3,10 @@ SET search_path TO local_shard_copy;
 SET client_min_messages TO DEBUG;
 SET citus.next_shard_id TO 1570000;
 SET citus.replicate_reference_tables_on_activate TO off;
-SELECT * FROM master_add_node('localhost', :master_port, groupid := 0);
- master_add_node
+SELECT 1 FROM master_add_node('localhost', :master_port, groupid := 0);
+ ?column?
 ---------------------------------------------------------------------
-              32
+        1
 (1 row)
 
 SET citus.shard_count TO 4;
@@ -485,7 +485,7 @@ NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shar
 
 -- shard creation should be done locally
 SELECT create_reference_table('ref_table');
-NOTICE:  executing the command locally: SELECT worker_apply_shard_ddl_command (1330000, 'local_shard_copy', 'CREATE TABLE local_shard_copy.ref_table (a integer)');SELECT worker_apply_shard_ddl_command (1330000, 'local_shard_copy', 'ALTER TABLE local_shard_copy.ref_table OWNER TO postgres')
+NOTICE:  executing the command locally: SELECT worker_apply_shard_ddl_command (1330000, 'local_shard_copy', 'CREATE TABLE local_shard_copy.ref_table (a integer) ');SELECT worker_apply_shard_ddl_command (1330000, 'local_shard_copy', 'ALTER TABLE local_shard_copy.ref_table OWNER TO postgres')
 NOTICE:  executing the copy locally for shard xxxxx
 NOTICE:  Copying data from local table...
 NOTICE:  copying the data has completed

src/test/regress/expected/local_shard_execution_dropped_column.out

@@ -0,0 +1,331 @@
+CREATE SCHEMA local_shard_execution_dropped_column;
+SET search_path TO local_shard_execution_dropped_column;
+SET citus.next_shard_id TO 2460000;
+-- the scenario is described on https://github.com/citusdata/citus/issues/5038
+-- first stop the metadata syncing to the node do that drop column
+-- is not propogated
+SELECT stop_metadata_sync_to_node('localhost',:worker_1_port);
+ stop_metadata_sync_to_node
+---------------------------------------------------------------------
+
+(1 row)
+
+SELECT stop_metadata_sync_to_node('localhost',:worker_2_port);
+ stop_metadata_sync_to_node
+---------------------------------------------------------------------
+
+(1 row)
+
+-- create a distributed table, drop a column and sync the metadata
+SET citus.shard_replication_factor TO 1;
+SET citus.replication_model TO streaming;
+CREATE TABLE t1 (a int, b int, c int UNIQUE);
+SELECT create_distributed_table('t1', 'c');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+ALTER TABLE t1 DROP COLUMN b;
+SELECT start_metadata_sync_to_node('localhost',:worker_1_port);
+ start_metadata_sync_to_node
+---------------------------------------------------------------------
+
+(1 row)
+
+SELECT start_metadata_sync_to_node('localhost',:worker_2_port);
+ start_metadata_sync_to_node
+---------------------------------------------------------------------
+
+(1 row)
+
+\c - - - :worker_1_port
+SET search_path TO local_shard_execution_dropped_column;
+-- show the dropped columns
+SELECT attrelid::regclass, attname, attnum, attisdropped
+FROM pg_attribute WHERE attrelid IN ('t1'::regclass, 't1_2460000'::regclass) and attname NOT IN ('tableoid','cmax', 'xmax', 'cmin', 'xmin', 'ctid')
+ORDER BY 1, 3, 2, 4;
+  attrelid  |           attname            | attnum | attisdropped
+---------------------------------------------------------------------
+ t1_2460000 | a                            |      1 | f
+ t1_2460000 | ........pg.dropped.2........ |      2 | t
+ t1_2460000 | c                            |      3 | f
+ t1         | a                            |      1 | f
+ t1         | c                            |      2 | f
+(5 rows)
+
+-- connect to a worker node where local execution is done
+prepare p1(int) as insert into t1(a,c) VALUES (5,$1) ON CONFLICT (c) DO NOTHING;
+SET citus.log_remote_commands TO ON;
+execute p1(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (a, c) VALUES (5, 8) ON CONFLICT(c) DO NOTHING
+execute p1(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (a, c) VALUES (5, 8) ON CONFLICT(c) DO NOTHING
+execute p1(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (a, c) VALUES (5, 8) ON CONFLICT(c) DO NOTHING
+execute p1(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (a, c) VALUES (5, 8) ON CONFLICT(c) DO NOTHING
+execute p1(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (a, c) VALUES (5, 8) ON CONFLICT(c) DO NOTHING
+execute p1(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (a, c) VALUES (5, 8) ON CONFLICT(c) DO NOTHING
+execute p1(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (a, c) VALUES (5, 8) ON CONFLICT(c) DO NOTHING
+execute p1(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (a, c) VALUES (5, 8) ON CONFLICT(c) DO NOTHING
+execute p1(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (a, c) VALUES (5, 8) ON CONFLICT(c) DO NOTHING
+execute p1(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (a, c) VALUES (5, 8) ON CONFLICT(c) DO NOTHING
+prepare p2(int) as SELECT count(*) FROM t1 WHERE c = $1 GROUP BY c;
+execute p2(8);
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shard_execution_dropped_column.t1_2460000 t1 WHERE (c OPERATOR(pg_catalog.=) 8) GROUP BY c
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+execute p2(8);
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shard_execution_dropped_column.t1_2460000 t1 WHERE (c OPERATOR(pg_catalog.=) 8) GROUP BY c
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+execute p2(8);
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shard_execution_dropped_column.t1_2460000 t1 WHERE (c OPERATOR(pg_catalog.=) 8) GROUP BY c
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+execute p2(8);
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shard_execution_dropped_column.t1_2460000 t1 WHERE (c OPERATOR(pg_catalog.=) 8) GROUP BY c
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+execute p2(8);
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shard_execution_dropped_column.t1_2460000 t1 WHERE (c OPERATOR(pg_catalog.=) 8) GROUP BY c
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+execute p2(8);
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shard_execution_dropped_column.t1_2460000 t1 WHERE (c OPERATOR(pg_catalog.=) 8) GROUP BY c
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+execute p2(8);
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shard_execution_dropped_column.t1_2460000 t1 WHERE (c OPERATOR(pg_catalog.=) 8) GROUP BY c
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+execute p2(8);
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shard_execution_dropped_column.t1_2460000 t1 WHERE (c OPERATOR(pg_catalog.=) 8) GROUP BY c
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+execute p2(8);
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shard_execution_dropped_column.t1_2460000 t1 WHERE (c OPERATOR(pg_catalog.=) 8) GROUP BY c
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+execute p2(8);
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shard_execution_dropped_column.t1_2460000 t1 WHERE (c OPERATOR(pg_catalog.=) 8) GROUP BY c
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+prepare p3(int) as INSERT INTO t1(a,c) VALUES (5, $1), (6, $1), (7, $1),(5, $1), (6, $1), (7, $1) ON CONFLICT DO NOTHING;
+execute p3(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (a, c) VALUES (5,8), (6,8), (7,8), (5,8), (6,8), (7,8) ON CONFLICT DO NOTHING
+execute p3(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (a, c) VALUES (5,8), (6,8), (7,8), (5,8), (6,8), (7,8) ON CONFLICT DO NOTHING
+execute p3(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (a, c) VALUES (5,8), (6,8), (7,8), (5,8), (6,8), (7,8) ON CONFLICT DO NOTHING
+execute p3(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (a, c) VALUES (5,8), (6,8), (7,8), (5,8), (6,8), (7,8) ON CONFLICT DO NOTHING
+execute p3(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (a, c) VALUES (5,8), (6,8), (7,8), (5,8), (6,8), (7,8) ON CONFLICT DO NOTHING
+execute p3(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (a, c) VALUES (5,8), (6,8), (7,8), (5,8), (6,8), (7,8) ON CONFLICT DO NOTHING
+execute p3(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (a, c) VALUES (5,8), (6,8), (7,8), (5,8), (6,8), (7,8) ON CONFLICT DO NOTHING
+execute p3(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (a, c) VALUES (5,8), (6,8), (7,8), (5,8), (6,8), (7,8) ON CONFLICT DO NOTHING
+execute p3(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (a, c) VALUES (5,8), (6,8), (7,8), (5,8), (6,8), (7,8) ON CONFLICT DO NOTHING
+execute p3(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (a, c) VALUES (5,8), (6,8), (7,8), (5,8), (6,8), (7,8) ON CONFLICT DO NOTHING
+prepare p4(int) as UPDATE t1 SET a = a + 1 WHERE c = $1;
+execute p4(8);
+NOTICE:  executing the command locally: UPDATE local_shard_execution_dropped_column.t1_2460000 t1 SET a = (a OPERATOR(pg_catalog.+) 1) WHERE (c OPERATOR(pg_catalog.=) 8)
+execute p4(8);
+NOTICE:  executing the command locally: UPDATE local_shard_execution_dropped_column.t1_2460000 t1 SET a = (a OPERATOR(pg_catalog.+) 1) WHERE (c OPERATOR(pg_catalog.=) 8)
+execute p4(8);
+NOTICE:  executing the command locally: UPDATE local_shard_execution_dropped_column.t1_2460000 t1 SET a = (a OPERATOR(pg_catalog.+) 1) WHERE (c OPERATOR(pg_catalog.=) 8)
+execute p4(8);
+NOTICE:  executing the command locally: UPDATE local_shard_execution_dropped_column.t1_2460000 t1 SET a = (a OPERATOR(pg_catalog.+) 1) WHERE (c OPERATOR(pg_catalog.=) 8)
+execute p4(8);
+NOTICE:  executing the command locally: UPDATE local_shard_execution_dropped_column.t1_2460000 t1 SET a = (a OPERATOR(pg_catalog.+) 1) WHERE (c OPERATOR(pg_catalog.=) 8)
+execute p4(8);
+NOTICE:  executing the command locally: UPDATE local_shard_execution_dropped_column.t1_2460000 t1 SET a = (a OPERATOR(pg_catalog.+) 1) WHERE (c OPERATOR(pg_catalog.=) 8)
+execute p4(8);
+NOTICE:  executing the command locally: UPDATE local_shard_execution_dropped_column.t1_2460000 t1 SET a = (a OPERATOR(pg_catalog.+) 1) WHERE (c OPERATOR(pg_catalog.=) 8)
+execute p4(8);
+NOTICE:  executing the command locally: UPDATE local_shard_execution_dropped_column.t1_2460000 t1 SET a = (a OPERATOR(pg_catalog.+) 1) WHERE (c OPERATOR(pg_catalog.=) 8)
+execute p4(8);
+NOTICE:  executing the command locally: UPDATE local_shard_execution_dropped_column.t1_2460000 t1 SET a = (a OPERATOR(pg_catalog.+) 1) WHERE (c OPERATOR(pg_catalog.=) 8)
+execute p4(8);
+NOTICE:  executing the command locally: UPDATE local_shard_execution_dropped_column.t1_2460000 t1 SET a = (a OPERATOR(pg_catalog.+) 1) WHERE (c OPERATOR(pg_catalog.=) 8)
+execute p4(8);
+NOTICE:  executing the command locally: UPDATE local_shard_execution_dropped_column.t1_2460000 t1 SET a = (a OPERATOR(pg_catalog.+) 1) WHERE (c OPERATOR(pg_catalog.=) 8)
+\c - - - :master_port
+-- one another combination is that the shell table
+-- has a dropped column but not the shard, via rebalance operation
+SET search_path TO local_shard_execution_dropped_column;
+ALTER TABLE t1 DROP COLUMN a;
+\c - - - :worker_1_port
+SET search_path TO local_shard_execution_dropped_column;
+-- show the dropped columns
+SELECT attrelid::regclass, attname, attnum, attisdropped
+FROM pg_attribute WHERE attrelid IN ('t1'::regclass, 't1_2460000'::regclass) and attname NOT IN ('tableoid','cmax', 'xmax', 'cmin', 'xmin', 'ctid')
+ORDER BY 1, 3, 2, 4;
+  attrelid  |           attname            | attnum | attisdropped
+---------------------------------------------------------------------
+ t1_2460000 | ........pg.dropped.1........ |      1 | t
+ t1_2460000 | ........pg.dropped.2........ |      2 | t
+ t1_2460000 | c                            |      3 | f
+ t1         | ........pg.dropped.1........ |      1 | t
+ t1         | c                            |      2 | f
+(5 rows)
+
+prepare p1(int) as insert into t1(c) VALUES ($1) ON CONFLICT (c) DO NOTHING;
+SET citus.log_remote_commands TO ON;
+execute p1(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (c) VALUES (8) ON CONFLICT(c) DO NOTHING
+execute p1(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (c) VALUES (8) ON CONFLICT(c) DO NOTHING
+execute p1(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (c) VALUES (8) ON CONFLICT(c) DO NOTHING
+execute p1(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (c) VALUES (8) ON CONFLICT(c) DO NOTHING
+execute p1(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (c) VALUES (8) ON CONFLICT(c) DO NOTHING
+execute p1(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (c) VALUES (8) ON CONFLICT(c) DO NOTHING
+execute p1(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (c) VALUES (8) ON CONFLICT(c) DO NOTHING
+execute p1(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (c) VALUES (8) ON CONFLICT(c) DO NOTHING
+execute p1(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (c) VALUES (8) ON CONFLICT(c) DO NOTHING
+execute p1(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (c) VALUES (8) ON CONFLICT(c) DO NOTHING
+prepare p2(int) as SELECT count(*) FROM t1 WHERE c = $1 GROUP BY c;
+execute p2(8);
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shard_execution_dropped_column.t1_2460000 t1 WHERE (c OPERATOR(pg_catalog.=) 8) GROUP BY c
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+execute p2(8);
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shard_execution_dropped_column.t1_2460000 t1 WHERE (c OPERATOR(pg_catalog.=) 8) GROUP BY c
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+execute p2(8);
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shard_execution_dropped_column.t1_2460000 t1 WHERE (c OPERATOR(pg_catalog.=) 8) GROUP BY c
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+execute p2(8);
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shard_execution_dropped_column.t1_2460000 t1 WHERE (c OPERATOR(pg_catalog.=) 8) GROUP BY c
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+execute p2(8);
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shard_execution_dropped_column.t1_2460000 t1 WHERE (c OPERATOR(pg_catalog.=) 8) GROUP BY c
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+execute p2(8);
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shard_execution_dropped_column.t1_2460000 t1 WHERE (c OPERATOR(pg_catalog.=) 8) GROUP BY c
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+execute p2(8);
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shard_execution_dropped_column.t1_2460000 t1 WHERE (c OPERATOR(pg_catalog.=) 8) GROUP BY c
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+execute p2(8);
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shard_execution_dropped_column.t1_2460000 t1 WHERE (c OPERATOR(pg_catalog.=) 8) GROUP BY c
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+execute p2(8);
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shard_execution_dropped_column.t1_2460000 t1 WHERE (c OPERATOR(pg_catalog.=) 8) GROUP BY c
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+execute p2(8);
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM local_shard_execution_dropped_column.t1_2460000 t1 WHERE (c OPERATOR(pg_catalog.=) 8) GROUP BY c
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+prepare p3(int) as INSERT INTO t1(c) VALUES ($1),($1),($1),($1),($1),($1),($1),($1),($1),($1),($1),($1),($1),($1) ON CONFLICT DO NOTHING;
+execute p3(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (c) VALUES (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8) ON CONFLICT DO NOTHING
+execute p3(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (c) VALUES (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8) ON CONFLICT DO NOTHING
+execute p3(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (c) VALUES (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8) ON CONFLICT DO NOTHING
+execute p3(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (c) VALUES (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8) ON CONFLICT DO NOTHING
+execute p3(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (c) VALUES (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8) ON CONFLICT DO NOTHING
+execute p3(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (c) VALUES (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8) ON CONFLICT DO NOTHING
+execute p3(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (c) VALUES (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8) ON CONFLICT DO NOTHING
+execute p3(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (c) VALUES (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8) ON CONFLICT DO NOTHING
+execute p3(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (c) VALUES (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8) ON CONFLICT DO NOTHING
+execute p3(8);
+NOTICE:  executing the command locally: INSERT INTO local_shard_execution_dropped_column.t1_2460000 AS citus_table_alias (c) VALUES (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8), (8) ON CONFLICT DO NOTHING
+\c - - - :master_port
+DROP SCHEMA local_shard_execution_dropped_column CASCADE;
+NOTICE:  drop cascades to table local_shard_execution_dropped_column.t1

src/test/regress/expected/master_update_table_statistics.out

@@ -0,0 +1,190 @@
+--
+-- master_update_table_statistics.sql
+--
+-- Test master_update_table_statistics function on both
+-- hash and append distributed tables
+-- This function updates shardlength, shardminvalue and shardmaxvalue
+--
+SET citus.next_shard_id TO 981000;
+SET citus.next_placement_id TO 982000;
+SET citus.shard_count TO 8;
+SET citus.shard_replication_factor TO 2;
+-- test with a hash-distributed table
+-- here we update only shardlength, not shardminvalue and shardmaxvalue
+CREATE TABLE test_table_statistics_hash (id int);
+SELECT create_distributed_table('test_table_statistics_hash', 'id');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- populate table
+INSERT INTO test_table_statistics_hash SELECT i FROM generate_series(0, 10000)i;
+-- originally shardlength (size of the shard) is zero
+SELECT
+    ds.logicalrelid::regclass::text AS tablename,
+    ds.shardid AS shardid,
+    dsp.placementid AS placementid,
+    shard_name(ds.logicalrelid, ds.shardid) AS shardname,
+    ds.shardminvalue AS shardminvalue,
+    ds.shardmaxvalue AS shardmaxvalue
+FROM pg_dist_shard ds JOIN pg_dist_shard_placement dsp USING (shardid)
+WHERE ds.logicalrelid::regclass::text in ('test_table_statistics_hash') AND dsp.shardlength = 0
+ORDER BY 2, 3;
+         tablename          | shardid | placementid |             shardname             | shardminvalue | shardmaxvalue
+---------------------------------------------------------------------
+ test_table_statistics_hash |  981000 |      982000 | test_table_statistics_hash_981000 | -2147483648   | -1610612737
+ test_table_statistics_hash |  981000 |      982001 | test_table_statistics_hash_981000 | -2147483648   | -1610612737
+ test_table_statistics_hash |  981001 |      982002 | test_table_statistics_hash_981001 | -1610612736   | -1073741825
+ test_table_statistics_hash |  981001 |      982003 | test_table_statistics_hash_981001 | -1610612736   | -1073741825
+ test_table_statistics_hash |  981002 |      982004 | test_table_statistics_hash_981002 | -1073741824   | -536870913
+ test_table_statistics_hash |  981002 |      982005 | test_table_statistics_hash_981002 | -1073741824   | -536870913
+ test_table_statistics_hash |  981003 |      982006 | test_table_statistics_hash_981003 | -536870912    | -1
+ test_table_statistics_hash |  981003 |      982007 | test_table_statistics_hash_981003 | -536870912    | -1
+ test_table_statistics_hash |  981004 |      982008 | test_table_statistics_hash_981004 | 0             | 536870911
+ test_table_statistics_hash |  981004 |      982009 | test_table_statistics_hash_981004 | 0             | 536870911
+ test_table_statistics_hash |  981005 |      982010 | test_table_statistics_hash_981005 | 536870912     | 1073741823
+ test_table_statistics_hash |  981005 |      982011 | test_table_statistics_hash_981005 | 536870912     | 1073741823
+ test_table_statistics_hash |  981006 |      982012 | test_table_statistics_hash_981006 | 1073741824    | 1610612735
+ test_table_statistics_hash |  981006 |      982013 | test_table_statistics_hash_981006 | 1073741824    | 1610612735
+ test_table_statistics_hash |  981007 |      982014 | test_table_statistics_hash_981007 | 1610612736    | 2147483647
+ test_table_statistics_hash |  981007 |      982015 | test_table_statistics_hash_981007 | 1610612736    | 2147483647
+(16 rows)
+
+-- setting this to on in order to verify that we use a distributed transaction id
+-- to run the size queries from different connections
+-- this is going to help detect deadlocks
+SET citus.log_remote_commands TO ON;
+-- setting this to sequential in order to have a deterministic order
+-- in the output of citus.log_remote_commands
+SET citus.multi_shard_modify_mode TO sequential;
+-- update table statistics and then check that shardlength has changed
+-- but shardminvalue and shardmaxvalue stay the same because this is
+-- a hash distributed table
+SELECT master_update_table_statistics('test_table_statistics_hash');
+NOTICE:  issuing BEGIN TRANSACTION ISOLATION LEVEL READ COMMITTED;SELECT assign_distributed_transaction_id(xx, xx, 'xxxxxxx');
+DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
+NOTICE:  issuing SELECT 981000 AS shard_id, NULL::text AS shard_minvalue, NULL::text AS shard_maxvalue, pg_relation_size('public.test_table_statistics_hash_981000') AS shard_size  UNION ALL SELECT 981001 AS shard_id, NULL::text AS shard_minvalue, NULL::text AS shard_maxvalue, pg_relation_size('public.test_table_statistics_hash_981001') AS shard_size  UNION ALL SELECT 981002 AS shard_id, NULL::text AS shard_minvalue, NULL::text AS shard_maxvalue, pg_relation_size('public.test_table_statistics_hash_981002') AS shard_size  UNION ALL SELECT 981003 AS shard_id, NULL::text AS shard_minvalue, NULL::text AS shard_maxvalue, pg_relation_size('public.test_table_statistics_hash_981003') AS shard_size  UNION ALL SELECT 981004 AS shard_id, NULL::text AS shard_minvalue, NULL::text AS shard_maxvalue, pg_relation_size('public.test_table_statistics_hash_981004') AS shard_size  UNION ALL SELECT 981005 AS shard_id, NULL::text AS shard_minvalue, NULL::text AS shard_maxvalue, pg_relation_size('public.test_table_statistics_hash_981005') AS shard_size  UNION ALL SELECT 981006 AS shard_id, NULL::text AS shard_minvalue, NULL::text AS shard_maxvalue, pg_relation_size('public.test_table_statistics_hash_981006') AS shard_size  UNION ALL SELECT 981007 AS shard_id, NULL::text AS shard_minvalue, NULL::text AS shard_maxvalue, pg_relation_size('public.test_table_statistics_hash_981007') AS shard_size  UNION ALL SELECT 0::bigint, NULL::text, NULL::text, 0::bigint;
+DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
+NOTICE:  issuing BEGIN TRANSACTION ISOLATION LEVEL READ COMMITTED;SELECT assign_distributed_transaction_id(xx, xx, 'xxxxxxx');
+DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
+NOTICE:  issuing SELECT 981000 AS shard_id, NULL::text AS shard_minvalue, NULL::text AS shard_maxvalue, pg_relation_size('public.test_table_statistics_hash_981000') AS shard_size  UNION ALL SELECT 981001 AS shard_id, NULL::text AS shard_minvalue, NULL::text AS shard_maxvalue, pg_relation_size('public.test_table_statistics_hash_981001') AS shard_size  UNION ALL SELECT 981002 AS shard_id, NULL::text AS shard_minvalue, NULL::text AS shard_maxvalue, pg_relation_size('public.test_table_statistics_hash_981002') AS shard_size  UNION ALL SELECT 981003 AS shard_id, NULL::text AS shard_minvalue, NULL::text AS shard_maxvalue, pg_relation_size('public.test_table_statistics_hash_981003') AS shard_size  UNION ALL SELECT 981004 AS shard_id, NULL::text AS shard_minvalue, NULL::text AS shard_maxvalue, pg_relation_size('public.test_table_statistics_hash_981004') AS shard_size  UNION ALL SELECT 981005 AS shard_id, NULL::text AS shard_minvalue, NULL::text AS shard_maxvalue, pg_relation_size('public.test_table_statistics_hash_981005') AS shard_size  UNION ALL SELECT 981006 AS shard_id, NULL::text AS shard_minvalue, NULL::text AS shard_maxvalue, pg_relation_size('public.test_table_statistics_hash_981006') AS shard_size  UNION ALL SELECT 981007 AS shard_id, NULL::text AS shard_minvalue, NULL::text AS shard_maxvalue, pg_relation_size('public.test_table_statistics_hash_981007') AS shard_size  UNION ALL SELECT 0::bigint, NULL::text, NULL::text, 0::bigint;
+DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
+NOTICE:  issuing COMMIT
+DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
+NOTICE:  issuing COMMIT
+DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
+ master_update_table_statistics
+---------------------------------------------------------------------
+
+(1 row)
+
+RESET citus.log_remote_commands;
+RESET citus.multi_shard_modify_mode;
+SELECT
+    ds.logicalrelid::regclass::text AS tablename,
+    ds.shardid AS shardid,
+    dsp.placementid AS placementid,
+    shard_name(ds.logicalrelid, ds.shardid) AS shardname,
+    ds.shardminvalue as shardminvalue,
+    ds.shardmaxvalue as shardmaxvalue
+FROM pg_dist_shard ds JOIN pg_dist_shard_placement dsp USING (shardid)
+WHERE ds.logicalrelid::regclass::text in ('test_table_statistics_hash') AND dsp.shardlength > 0
+ORDER BY 2, 3;
+         tablename          | shardid | placementid |             shardname             | shardminvalue | shardmaxvalue
+---------------------------------------------------------------------
+ test_table_statistics_hash |  981000 |      982000 | test_table_statistics_hash_981000 | -2147483648   | -1610612737
+ test_table_statistics_hash |  981000 |      982001 | test_table_statistics_hash_981000 | -2147483648   | -1610612737
+ test_table_statistics_hash |  981001 |      982002 | test_table_statistics_hash_981001 | -1610612736   | -1073741825
+ test_table_statistics_hash |  981001 |      982003 | test_table_statistics_hash_981001 | -1610612736   | -1073741825
+ test_table_statistics_hash |  981002 |      982004 | test_table_statistics_hash_981002 | -1073741824   | -536870913
+ test_table_statistics_hash |  981002 |      982005 | test_table_statistics_hash_981002 | -1073741824   | -536870913
+ test_table_statistics_hash |  981003 |      982006 | test_table_statistics_hash_981003 | -536870912    | -1
+ test_table_statistics_hash |  981003 |      982007 | test_table_statistics_hash_981003 | -536870912    | -1
+ test_table_statistics_hash |  981004 |      982008 | test_table_statistics_hash_981004 | 0             | 536870911
+ test_table_statistics_hash |  981004 |      982009 | test_table_statistics_hash_981004 | 0             | 536870911
+ test_table_statistics_hash |  981005 |      982010 | test_table_statistics_hash_981005 | 536870912     | 1073741823
+ test_table_statistics_hash |  981005 |      982011 | test_table_statistics_hash_981005 | 536870912     | 1073741823
+ test_table_statistics_hash |  981006 |      982012 | test_table_statistics_hash_981006 | 1073741824    | 1610612735
+ test_table_statistics_hash |  981006 |      982013 | test_table_statistics_hash_981006 | 1073741824    | 1610612735
+ test_table_statistics_hash |  981007 |      982014 | test_table_statistics_hash_981007 | 1610612736    | 2147483647
+ test_table_statistics_hash |  981007 |      982015 | test_table_statistics_hash_981007 | 1610612736    | 2147483647
+(16 rows)
+
+-- check with an append-distributed table
+-- here we update shardlength, shardminvalue and shardmaxvalue
+CREATE TABLE test_table_statistics_append (id int);
+SELECT create_distributed_table('test_table_statistics_append', 'id', 'append');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+COPY test_table_statistics_append FROM PROGRAM 'echo 0 && echo 1 && echo 2 && echo 3' WITH CSV;
+COPY test_table_statistics_append FROM PROGRAM 'echo 4 && echo 5 && echo 6 && echo 7' WITH CSV;
+-- originally shardminvalue and shardmaxvalue will be 0,3 and 4, 7
+SELECT
+    ds.logicalrelid::regclass::text AS tablename,
+    ds.shardid AS shardid,
+    dsp.placementid AS placementid,
+    shard_name(ds.logicalrelid, ds.shardid) AS shardname,
+    ds.shardminvalue as shardminvalue,
+    ds.shardmaxvalue as shardmaxvalue
+FROM pg_dist_shard ds JOIN pg_dist_shard_placement dsp USING (shardid)
+WHERE ds.logicalrelid::regclass::text in ('test_table_statistics_append')
+ORDER BY 2, 3;
+          tablename           | shardid | placementid |              shardname              | shardminvalue | shardmaxvalue
+---------------------------------------------------------------------
+ test_table_statistics_append |  981008 |      982016 | test_table_statistics_append_981008 | 0             | 3
+ test_table_statistics_append |  981008 |      982017 | test_table_statistics_append_981008 | 0             | 3
+ test_table_statistics_append |  981009 |      982018 | test_table_statistics_append_981009 | 4             | 7
+ test_table_statistics_append |  981009 |      982019 | test_table_statistics_append_981009 | 4             | 7
+(4 rows)
+
+-- delete some data to change shardminvalues of a shards
+DELETE FROM test_table_statistics_append WHERE id = 0 OR id = 4;
+SET citus.log_remote_commands TO ON;
+SET citus.multi_shard_modify_mode TO sequential;
+-- update table statistics and then check that shardminvalue has changed
+-- shardlength (shardsize) is still 8192 since there is very few data
+SELECT master_update_table_statistics('test_table_statistics_append');
+NOTICE:  issuing BEGIN TRANSACTION ISOLATION LEVEL READ COMMITTED;SELECT assign_distributed_transaction_id(xx, xx, 'xxxxxxx');
+DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
+NOTICE:  issuing SELECT 981008 AS shard_id, min(id)::text AS shard_minvalue, max(id)::text AS shard_maxvalue, pg_relation_size('public.test_table_statistics_append_981008') AS shard_size FROM test_table_statistics_append_981008  UNION ALL SELECT 981009 AS shard_id, min(id)::text AS shard_minvalue, max(id)::text AS shard_maxvalue, pg_relation_size('public.test_table_statistics_append_981009') AS shard_size FROM test_table_statistics_append_981009  UNION ALL SELECT 0::bigint, NULL::text, NULL::text, 0::bigint;
+DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
+NOTICE:  issuing BEGIN TRANSACTION ISOLATION LEVEL READ COMMITTED;SELECT assign_distributed_transaction_id(xx, xx, 'xxxxxxx');
+DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
+NOTICE:  issuing SELECT 981008 AS shard_id, min(id)::text AS shard_minvalue, max(id)::text AS shard_maxvalue, pg_relation_size('public.test_table_statistics_append_981008') AS shard_size FROM test_table_statistics_append_981008  UNION ALL SELECT 981009 AS shard_id, min(id)::text AS shard_minvalue, max(id)::text AS shard_maxvalue, pg_relation_size('public.test_table_statistics_append_981009') AS shard_size FROM test_table_statistics_append_981009  UNION ALL SELECT 0::bigint, NULL::text, NULL::text, 0::bigint;
+DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
+NOTICE:  issuing COMMIT
+DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
+NOTICE:  issuing COMMIT
+DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
+ master_update_table_statistics
+---------------------------------------------------------------------
+
+(1 row)
+
+RESET citus.log_remote_commands;
+RESET citus.multi_shard_modify_mode;
+SELECT
+    ds.logicalrelid::regclass::text AS tablename,
+    ds.shardid AS shardid,
+    dsp.placementid AS placementid,
+    shard_name(ds.logicalrelid, ds.shardid) AS shardname,
+    ds.shardminvalue as shardminvalue,
+    ds.shardmaxvalue as shardmaxvalue
+FROM pg_dist_shard ds JOIN pg_dist_shard_placement dsp USING (shardid)
+WHERE ds.logicalrelid::regclass::text in ('test_table_statistics_append')
+ORDER BY 2, 3;
+          tablename           | shardid | placementid |              shardname              | shardminvalue | shardmaxvalue
+---------------------------------------------------------------------
+ test_table_statistics_append |  981008 |      982016 | test_table_statistics_append_981008 | 1             | 3
+ test_table_statistics_append |  981008 |      982017 | test_table_statistics_append_981008 | 1             | 3
+ test_table_statistics_append |  981009 |      982018 | test_table_statistics_append_981009 | 5             | 7
+ test_table_statistics_append |  981009 |      982019 | test_table_statistics_append_981009 | 5             | 7
+(4 rows)
+
+DROP TABLE test_table_statistics_hash, test_table_statistics_append;
+ALTER SYSTEM RESET citus.shard_count;
+ALTER SYSTEM RESET citus.shard_replication_factor;

src/test/regress/expected/multi_extension.out

@@ -406,6 +406,105 @@ SELECT * FROM print_extension_changes();
                  | function worker_save_query_explain_analyze(text,jsonb)
 (2 rows)
 
+-- Test upgrade paths for backported citus_pg_upgrade functions
+ALTER EXTENSION citus UPDATE TO '9.4-2';
+ALTER EXTENSION citus UPDATE TO '9.4-1';
+-- Should be empty result, even though the downgrade doesn't undo the upgrade, the
+-- function signature doesn't change, which is reflected here.
+SELECT * FROM print_extension_changes();
+ previous_object | current_object
+---------------------------------------------------------------------
+(0 rows)
+
+ALTER EXTENSION citus UPDATE TO '9.4-2';
+SELECT * FROM print_extension_changes();
+ previous_object | current_object
+---------------------------------------------------------------------
+(0 rows)
+
+-- Snapshot of state at 9.4-1
+ALTER EXTENSION citus UPDATE TO '9.4-1';
+SELECT * FROM print_extension_changes();
+ previous_object | current_object
+---------------------------------------------------------------------
+(0 rows)
+
+-- Test upgrade paths for backported improvement of master_update_table_statistics function
+ALTER EXTENSION citus UPDATE TO '9.4-3';
+-- should see the new source code with internal function citus_update_table_statistics
+SELECT prosrc FROM pg_proc WHERE proname = 'master_update_table_statistics' ORDER BY 1;
+            prosrc
+---------------------------------------------------------------------
+ citus_update_table_statistics
+(1 row)
+
+ALTER EXTENSION citus UPDATE TO '9.4-2';
+-- should see the old source code
+SELECT prosrc FROM pg_proc WHERE proname = 'master_update_table_statistics' ORDER BY 1;
+                               prosrc
+---------------------------------------------------------------------
+                                                                   +
+ DECLARE                                                           +
+  colocated_tables regclass[];                                     +
+ BEGIN                                                             +
+  SELECT get_colocated_table_array(relation) INTO colocated_tables;+
+  PERFORM                                                          +
+   master_update_shard_statistics(shardid)                         +
+  FROM                                                             +
+   pg_dist_shard                                                   +
+  WHERE                                                            +
+   logicalrelid = ANY (colocated_tables);                          +
+ END;                                                              +
+
+(1 row)
+
+-- Should be empty result
+SELECT * FROM print_extension_changes();
+ previous_object | current_object
+---------------------------------------------------------------------
+(0 rows)
+
+ALTER EXTENSION citus UPDATE TO '9.4-3';
+-- should see the new source code with internal function citus_update_table_statistics
+SELECT prosrc FROM pg_proc WHERE proname = 'master_update_table_statistics' ORDER BY 1;
+            prosrc
+---------------------------------------------------------------------
+ citus_update_table_statistics
+(1 row)
+
+-- Should be empty result
+SELECT * FROM print_extension_changes();
+ previous_object | current_object
+---------------------------------------------------------------------
+(0 rows)
+
+-- Snapshot of state at 9.4-1
+ALTER EXTENSION citus UPDATE TO '9.4-1';
+-- should see the old source code
+SELECT prosrc FROM pg_proc WHERE proname = 'master_update_table_statistics' ORDER BY 1;
+                               prosrc
+---------------------------------------------------------------------
+                                                                   +
+ DECLARE                                                           +
+  colocated_tables regclass[];                                     +
+ BEGIN                                                             +
+  SELECT get_colocated_table_array(relation) INTO colocated_tables;+
+  PERFORM                                                          +
+   master_update_shard_statistics(shardid)                         +
+  FROM                                                             +
+   pg_dist_shard                                                   +
+  WHERE                                                            +
+   logicalrelid = ANY (colocated_tables);                          +
+ END;                                                              +
+
+(1 row)
+
+-- Should be empty result
+SELECT * FROM print_extension_changes();
+ previous_object | current_object
+---------------------------------------------------------------------
+(0 rows)
+
 -- Test downgrade to 9.4-1 from 9.5-1
 ALTER EXTENSION citus UPDATE TO '9.5-1';
 BEGIN;
@@ -453,12 +552,111 @@ SELECT * FROM print_extension_changes();
                                                                      | function worker_record_sequence_dependency(regclass,regclass,name)
 (10 rows)
 
+-- Test upgrade paths for backported citus_pg_upgrade functions
+ALTER EXTENSION citus UPDATE TO '9.5-2';
+ALTER EXTENSION citus UPDATE TO '9.5-1';
+-- Should be empty result, even though the downgrade doesn't undo the upgrade, the
+-- function signature doesn't change, which is reflected here.
+SELECT * FROM print_extension_changes();
+ previous_object | current_object
+---------------------------------------------------------------------
+(0 rows)
+
+ALTER EXTENSION citus UPDATE TO '9.5-2';
+SELECT * FROM print_extension_changes();
+ previous_object | current_object
+---------------------------------------------------------------------
+(0 rows)
+
+-- Snapshot of state at 9.5-1
+ALTER EXTENSION citus UPDATE TO '9.5-1';
+SELECT * FROM print_extension_changes();
+ previous_object | current_object
+---------------------------------------------------------------------
+(0 rows)
+
+-- Test upgrade paths for backported improvement of master_update_table_statistics function
+ALTER EXTENSION citus UPDATE TO '9.5-3';
+-- should see the new source code with internal function citus_update_table_statistics
+SELECT prosrc FROM pg_proc WHERE proname = 'master_update_table_statistics' ORDER BY 1;
+            prosrc
+---------------------------------------------------------------------
+ citus_update_table_statistics
+(1 row)
+
+ALTER EXTENSION citus UPDATE TO '9.5-2';
+-- should see the old source code
+SELECT prosrc FROM pg_proc WHERE proname = 'master_update_table_statistics' ORDER BY 1;
+                               prosrc
+---------------------------------------------------------------------
+                                                                   +
+ DECLARE                                                           +
+  colocated_tables regclass[];                                     +
+ BEGIN                                                             +
+  SELECT get_colocated_table_array(relation) INTO colocated_tables;+
+  PERFORM                                                          +
+   master_update_shard_statistics(shardid)                         +
+  FROM                                                             +
+   pg_dist_shard                                                   +
+  WHERE                                                            +
+   logicalrelid = ANY (colocated_tables);                          +
+ END;                                                              +
+
+(1 row)
+
+-- Should be empty result
+SELECT * FROM print_extension_changes();
+ previous_object | current_object
+---------------------------------------------------------------------
+(0 rows)
+
+ALTER EXTENSION citus UPDATE TO '9.5-3';
+-- should see the new source code with internal function citus_update_table_statistics
+SELECT prosrc FROM pg_proc WHERE proname = 'master_update_table_statistics' ORDER BY 1;
+            prosrc
+---------------------------------------------------------------------
+ citus_update_table_statistics
+(1 row)
+
+-- Should be empty result
+SELECT * FROM print_extension_changes();
+ previous_object | current_object
+---------------------------------------------------------------------
+(0 rows)
+
+-- Snapshot of state at 9.5-1
+ALTER EXTENSION citus UPDATE TO '9.5-1';
+-- should see the old source code
+SELECT prosrc FROM pg_proc WHERE proname = 'master_update_table_statistics' ORDER BY 1;
+                               prosrc
+---------------------------------------------------------------------
+                                                                   +
+ DECLARE                                                           +
+  colocated_tables regclass[];                                     +
+ BEGIN                                                             +
+  SELECT get_colocated_table_array(relation) INTO colocated_tables;+
+  PERFORM                                                          +
+   master_update_shard_statistics(shardid)                         +
+  FROM                                                             +
+   pg_dist_shard                                                   +
+  WHERE                                                            +
+   logicalrelid = ANY (colocated_tables);                          +
+ END;                                                              +
+
+(1 row)
+
+-- Should be empty result
+SELECT * FROM print_extension_changes();
+ previous_object | current_object
+---------------------------------------------------------------------
+(0 rows)
+
 DROP TABLE prev_objects, extension_diff;
 -- show running version
 SHOW citus.version;
  citus.version
 ---------------------------------------------------------------------
- 9.5devel
+ 9.5.12
 (1 row)
 
 -- ensure no objects were created outside pg_catalog

src/test/regress/expected/multi_follower_dml.out

@@ -269,7 +269,7 @@ ERROR:  writing to worker nodes is not currently allowed
 DETAIL:  citus.use_secondary_nodes is set to 'always'
 SELECT * FROM citus_local_table ORDER BY a;
 ERROR:  there is a shard placement in node group 0 but there are no nodes in that group
-\c - - - :master_port
+\c -reuse-previous=off regression - - :master_port
 DROP TABLE the_table;
 DROP TABLE reference_table;
 DROP TABLE citus_local_table;

src/test/regress/expected/multi_follower_select_statements.out

@@ -77,7 +77,7 @@ order by s_i_id;
 SELECT * FROM the_table;
 ERROR:  node group does not have a secondary node
 -- add the secondary nodes and try again, the SELECT statement should work this time
-\c - - - :master_port
+\c -reuse-previous=off regression - - :master_port
 SELECT 1 FROM master_add_node('localhost', :follower_worker_1_port,
   groupid => (SELECT groupid FROM pg_dist_node WHERE nodeport = :worker_1_port),
   noderole => 'secondary');
@@ -149,7 +149,7 @@ order by s_i_id;
 ERROR:  there is a shard placement in node group but there are no nodes in that group
 -- now move the secondary nodes into the new cluster and see that the follower, finally
 -- correctly configured, can run select queries involving them
-\c - - - :master_port
+\c -reuse-previous=off regression - - :master_port
 UPDATE pg_dist_node SET nodecluster = 'second-cluster' WHERE noderole = 'secondary';
 \c "port=9070 dbname=regression options='-c\ citus.use_secondary_nodes=always\ -c\ citus.cluster_name=second-cluster'"
 SELECT * FROM the_table;
@@ -160,6 +160,6 @@ SELECT * FROM the_table;
 (2 rows)
 
 -- clean up after ourselves
-\c - - - :master_port
+\c -reuse-previous=off regression - - :master_port
 DROP TABLE the_table;
 DROP TABLE stock;

src/test/regress/expected/multi_foreign_key.out

@@ -938,5 +938,239 @@ SELECT create_reference_table('self_referencing_reference_table');
 (1 row)
 
 ALTER TABLE self_referencing_reference_table ADD CONSTRAINT fk FOREIGN KEY(id, other_column_ref) REFERENCES self_referencing_reference_table(id, other_column);
+-- make sure that if fkey is dropped
+-- Citus can see up-to date fkey graph
+CREATE TABLE dropfkeytest1 (x int unique);
+CREATE TABLE dropfkeytest2 (x int8);
+ALTER TABLE dropfkeytest2 ADD CONSTRAINT fkey1 FOREIGN KEY (x) REFERENCES dropfkeytest1(x);
+SELECT create_distributed_table ('dropfkeytest1', 'x');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- this should error out
+SELECT create_distributed_table ('dropfkeytest2', 'x', colocate_with:='none');
+ERROR:  cannot create foreign key constraint since relations are not colocated or not referencing a reference table
+DETAIL:  A distributed table can only have foreign keys if it is referencing another colocated hash distributed table or a reference table
+ALTER TABLE dropfkeytest2 DROP CONSTRAINT fkey1;
+-- this should work
+SELECT create_distributed_table ('dropfkeytest2', 'x', colocate_with:='none');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+DROP TABLE dropfkeytest1, dropfkeytest2 CASCADE;
+-- make sure that if a column that is in a fkey is dropped
+-- Citus can see up-to date fkey graph
+CREATE TABLE dropfkeytest1 (x int unique);
+CREATE TABLE dropfkeytest2 (x int8, y int8);
+ALTER TABLE dropfkeytest2 ADD CONSTRAINT fkey1 FOREIGN KEY (y) REFERENCES dropfkeytest1(x);
+SELECT create_distributed_table ('dropfkeytest1', 'x');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- this should error out
+SELECT create_distributed_table ('dropfkeytest2', 'y', colocate_with:='none');
+ERROR:  cannot create foreign key constraint since relations are not colocated or not referencing a reference table
+DETAIL:  A distributed table can only have foreign keys if it is referencing another colocated hash distributed table or a reference table
+ALTER TABLE dropfkeytest2 DROP COLUMN y;
+-- this should work
+SELECT create_distributed_table ('dropfkeytest2', 'x', colocate_with:='none');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+DROP TABLE dropfkeytest1, dropfkeytest2 CASCADE;
+-- make sure that even if a column that is in a multi-column index is dropped
+-- Citus can see up-to date fkey graph
+CREATE TABLE dropfkeytest1 (x int, y int);
+CREATE UNIQUE INDEX indd ON dropfkeytest1(x, y);
+CREATE TABLE dropfkeytest2 (x int8, y int8);
+ALTER TABLE dropfkeytest2 ADD CONSTRAINT fkey1 FOREIGN KEY (x, y) REFERENCES dropfkeytest1(x, y);
+SELECT create_distributed_table ('dropfkeytest1', 'x');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- this should error out
+SELECT create_distributed_table ('dropfkeytest2', 'y', colocate_with:='none');
+ERROR:  cannot create foreign key constraint since relations are not colocated or not referencing a reference table
+DETAIL:  A distributed table can only have foreign keys if it is referencing another colocated hash distributed table or a reference table
+ALTER TABLE dropfkeytest2 DROP COLUMN y CASCADE;
+-- this should work
+SELECT create_distributed_table ('dropfkeytest2', 'x', colocate_with:='none');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+DROP TABLE dropfkeytest1, dropfkeytest2 CASCADE;
+-- make sure that even if a column that is in a multi-column fkey is dropped
+-- Citus can see up-to date fkey graph
+CREATE TABLE dropfkeytest1 (x int, y int);
+CREATE UNIQUE INDEX indd ON dropfkeytest1(x, y);
+CREATE TABLE dropfkeytest2 (x int8, y int8);
+ALTER TABLE dropfkeytest2 ADD CONSTRAINT fkey1 FOREIGN KEY (x, y) REFERENCES dropfkeytest1(x, y);
+SELECT create_distributed_table ('dropfkeytest1', 'x');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- this should error out
+SELECT create_distributed_table ('dropfkeytest2', 'y', colocate_with:='none');
+ERROR:  cannot create foreign key constraint since relations are not colocated or not referencing a reference table
+DETAIL:  A distributed table can only have foreign keys if it is referencing another colocated hash distributed table or a reference table
+ALTER TABLE dropfkeytest1 DROP COLUMN y CASCADE;
+NOTICE:  drop cascades to constraint fkey1 on table dropfkeytest2
+-- this should work
+SELECT create_distributed_table ('dropfkeytest2', 'x', colocate_with:='none');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+DROP TABLE dropfkeytest1, dropfkeytest2 CASCADE;
+-- make sure that even if an index which fkey relies on is dropped
+-- Citus can see up-to date fkey graph
+-- also irrelevant index drops doesn't affect this
+CREATE TABLE dropfkeytest1 (x int);
+CREATE UNIQUE INDEX i1 ON dropfkeytest1(x);
+CREATE UNIQUE INDEX unrelated_idx ON dropfkeytest1(x);
+CREATE TABLE dropfkeytest2 (x int8, y int8);
+ALTER TABLE dropfkeytest2 ADD CONSTRAINT fkey1 FOREIGN KEY (y) REFERENCES dropfkeytest1(x);
+SELECT create_distributed_table ('dropfkeytest1', 'x');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- this should error out
+SELECT create_distributed_table ('dropfkeytest2', 'y', colocate_with:='none');
+ERROR:  cannot create foreign key constraint since relations are not colocated or not referencing a reference table
+DETAIL:  A distributed table can only have foreign keys if it is referencing another colocated hash distributed table or a reference table
+DROP INDEX unrelated_idx CASCADE;
+-- should still error out since we didn't drop the index that foreign key depends on
+SELECT create_distributed_table ('dropfkeytest2', 'x', colocate_with:='none');
+ERROR:  cannot create foreign key constraint since relations are not colocated or not referencing a reference table
+DETAIL:  A distributed table can only have foreign keys if it is referencing another colocated hash distributed table or a reference table
+DROP INDEX i1 CASCADE;
+NOTICE:  drop cascades to constraint fkey1 on table dropfkeytest2
+-- this should work
+SELECT create_distributed_table ('dropfkeytest2', 'x', colocate_with:='none');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+DROP TABLE dropfkeytest1, dropfkeytest2 CASCADE;
+-- make sure that even if a uniqueness constraint which fkey depends on is dropped
+-- Citus can see up-to date fkey graph
+CREATE TABLE dropfkeytest1 (x int unique);
+CREATE TABLE dropfkeytest2 (x int8, y int8);
+ALTER TABLE dropfkeytest2 ADD CONSTRAINT fkey1 FOREIGN KEY (y) REFERENCES dropfkeytest1(x);
+SELECT create_distributed_table ('dropfkeytest1', 'x');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- this should error out
+SELECT create_distributed_table ('dropfkeytest2', 'y', colocate_with:='none');
+ERROR:  cannot create foreign key constraint since relations are not colocated or not referencing a reference table
+DETAIL:  A distributed table can only have foreign keys if it is referencing another colocated hash distributed table or a reference table
+ALTER TABLE dropfkeytest1 DROP CONSTRAINT dropfkeytest1_x_key CASCADE;
+NOTICE:  drop cascades to constraint fkey1 on table dropfkeytest2
+-- this should work
+SELECT create_distributed_table ('dropfkeytest2', 'x', colocate_with:='none');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+DROP TABLE dropfkeytest1, dropfkeytest2 CASCADE;
+-- make sure that even if a primary key which fkey depends on is dropped
+-- Citus can see up-to date fkey graph
+CREATE TABLE dropfkeytest1 (x int primary key);
+CREATE TABLE dropfkeytest2 (x int8, y int8);
+ALTER TABLE dropfkeytest2 ADD CONSTRAINT fkey1 FOREIGN KEY (y) REFERENCES dropfkeytest1(x);
+SELECT create_distributed_table ('dropfkeytest1', 'x');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- this should error out
+SELECT create_distributed_table ('dropfkeytest2', 'y', colocate_with:='none');
+ERROR:  cannot create foreign key constraint since relations are not colocated or not referencing a reference table
+DETAIL:  A distributed table can only have foreign keys if it is referencing another colocated hash distributed table or a reference table
+ALTER TABLE dropfkeytest1 DROP CONSTRAINT dropfkeytest1_pkey CASCADE;
+NOTICE:  drop cascades to constraint fkey1 on table dropfkeytest2
+-- this should work
+SELECT create_distributed_table ('dropfkeytest2', 'x', colocate_with:='none');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+DROP TABLE dropfkeytest1, dropfkeytest2 CASCADE;
+-- make sure that even if a schema which fkey depends on is dropped
+-- Citus can see up-to date fkey graph
+CREATE SCHEMA fkeytestsc;
+CREATE TABLE fkeytestsc.dropfkeytest1 (x int unique);
+CREATE TABLE dropfkeytest2 (x int8, y int8);
+ALTER TABLE dropfkeytest2 ADD CONSTRAINT fkey1 FOREIGN KEY (y) REFERENCES fkeytestsc.dropfkeytest1(x);
+SELECT create_distributed_table ('fkeytestsc.dropfkeytest1', 'x');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- this should error out
+SELECT create_distributed_table ('dropfkeytest2', 'y', colocate_with:='none');
+ERROR:  cannot create foreign key constraint since relations are not colocated or not referencing a reference table
+DETAIL:  A distributed table can only have foreign keys if it is referencing another colocated hash distributed table or a reference table
+DROP SCHEMA fkeytestsc CASCADE;
+NOTICE:  drop cascades to 2 other objects
+DETAIL:  drop cascades to table fkeytestsc.dropfkeytest1
+drop cascades to constraint fkey1 on table dropfkeytest2
+-- this should work
+SELECT create_distributed_table ('dropfkeytest2', 'x', colocate_with:='none');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+DROP TABLE dropfkeytest2 CASCADE;
+-- make sure that even if a table which fkey depends on is dropped
+-- Citus can see up-to date fkey graph
+CREATE TABLE dropfkeytest1 (x int unique);
+CREATE TABLE dropfkeytest2 (x int8, y int8);
+ALTER TABLE dropfkeytest2 ADD CONSTRAINT fkey1 FOREIGN KEY (y) REFERENCES dropfkeytest1(x);
+SELECT create_distributed_table ('dropfkeytest1', 'x');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- this should error out
+SELECT create_distributed_table ('dropfkeytest2', 'y', colocate_with:='none');
+ERROR:  cannot create foreign key constraint since relations are not colocated or not referencing a reference table
+DETAIL:  A distributed table can only have foreign keys if it is referencing another colocated hash distributed table or a reference table
+DROP TABLE dropfkeytest1 CASCADE;
+NOTICE:  drop cascades to constraint fkey1 on table dropfkeytest2
+-- this should work
+SELECT create_distributed_table ('dropfkeytest2', 'x', colocate_with:='none');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
 -- we no longer need those tables
-DROP TABLE referenced_by_reference_table, references_to_reference_table, reference_table, reference_table_second, referenced_local_table, self_referencing_reference_table;
+DROP TABLE referenced_by_reference_table, references_to_reference_table, reference_table, reference_table_second, referenced_local_table, self_referencing_reference_table, dropfkeytest2;

src/test/regress/expected/multi_join_pruning.out

@@ -38,14 +38,48 @@ DEBUG:  Router planner does not support append-partitioned tables.
 -- Partition pruning left three shards for the lineitem and one shard for the
 -- orders table. These shard sets don't overlap, so join pruning should prune
 -- out all the shards, and leave us with an empty task list.
+select * from pg_dist_shard
+where logicalrelid='lineitem'::regclass or
+	  logicalrelid='orders'::regclass
+order by shardid;
+ logicalrelid | shardid | shardstorage | shardminvalue | shardmaxvalue
+---------------------------------------------------------------------
+ lineitem     |  290000 | t            | 1             | 5986
+ lineitem     |  290001 | t            | 8997          | 14947
+ orders       |  290002 | t            | 1             | 5986
+ orders       |  290003 | t            | 8997          | 14947
+(4 rows)
+
+set citus.explain_distributed_queries to on;
+-- explain the query before actually executing it
+EXPLAIN SELECT sum(l_linenumber), avg(l_linenumber) FROM lineitem, orders
+	WHERE l_orderkey = o_orderkey AND l_orderkey > 6000 AND o_orderkey < 6000;
+DEBUG:  Router planner does not support append-partitioned tables.
+DEBUG:  join prunable for intervals [8997,14947] and [1,5986]
+                                 QUERY PLAN
+---------------------------------------------------------------------
+ Aggregate  (cost=750.01..750.02 rows=1 width=40)
+   ->  Custom Scan (Citus Adaptive)  (cost=0.00..0.00 rows=100000 width=24)
+         Task Count: 0
+         Tasks Shown: All
+(4 rows)
+
+set citus.explain_distributed_queries to off;
+set client_min_messages to debug3;
 SELECT sum(l_linenumber), avg(l_linenumber) FROM lineitem, orders
 	WHERE l_orderkey = o_orderkey AND l_orderkey > 6000 AND o_orderkey < 6000;
 DEBUG:  Router planner does not support append-partitioned tables.
+DEBUG:  constraint (gt) value: '6000'::bigint
+DEBUG:  shard count: 1
+DEBUG:  constraint (lt) value: '6000'::bigint
+DEBUG:  shard count: 1
+DEBUG:  join prunable for intervals [8997,14947] and [1,5986]
  sum | avg
 ---------------------------------------------------------------------
      |
 (1 row)
 
+set client_min_messages to debug2;
 -- Make sure that we can handle filters without a column
 SELECT sum(l_linenumber), avg(l_linenumber) FROM lineitem, orders
 	WHERE l_orderkey = o_orderkey AND false;

src/test/regress/expected/multi_multiuser.out

@@ -692,6 +692,39 @@ SELECT worker_fetch_partition_file(42, 1, 1, 1, 'localhost', :worker_1_port);
 (1 row)
 
 RESET ROLE;
+-- non-superuser should be able to use worker_append_table_to_shard on their own shard
+SET ROLE full_access;
+CREATE TABLE full_access_user_schema.source_table (id int);
+INSERT INTO full_access_user_schema.source_table VALUES (1);
+CREATE TABLE full_access_user_schema.shard_0 (id int);
+SELECT worker_append_table_to_shard('full_access_user_schema.shard_0', 'full_access_user_schema.source_table', 'localhost', :worker_2_port);
+ worker_append_table_to_shard
+---------------------------------------------------------------------
+
+(1 row)
+
+SELECT * FROM full_access_user_schema.shard_0;
+ id
+---------------------------------------------------------------------
+  1
+(1 row)
+
+RESET ROLE;
+-- other users should not be able to read from a table they have no access to via worker_append_table_to_shard
+SET ROLE usage_access;
+SELECT worker_append_table_to_shard('full_access_user_schema.shard_0', 'full_access_user_schema.source_table', 'localhost', :worker_2_port);
+WARNING:  permission denied for table source_table
+CONTEXT:  while executing command on localhost:xxxxx
+ERROR:  could not copy table "source_table" from "localhost:xxxxx"
+RESET ROLE;
+-- allow usage_access to read from table
+GRANT SELECT ON full_access_user_schema.source_table TO usage_access;
+-- other users should not be able to write to a table they do not have write access to
+SET ROLE usage_access;
+SELECT worker_append_table_to_shard('full_access_user_schema.shard_0', 'full_access_user_schema.source_table', 'localhost', :worker_2_port);
+ERROR:  permission denied for table shard_0
+RESET ROLE;
+DROP TABLE full_access_user_schema.source_table, full_access_user_schema.shard_0;
 -- now we will test that only the user who owns the fetched file is able to merge it into
 -- a table
 -- test that no other user can merge the downloaded file before the task is being tracked

src/test/regress/expected/multi_mx_node_metadata.out

@@ -21,6 +21,27 @@ CREATE FUNCTION mark_node_readonly(hostname TEXT, port INTEGER, isreadonly BOOLE
         master_run_on_worker(ARRAY[hostname], ARRAY[port],
                              ARRAY['SELECT pg_reload_conf()'], false);
 $$;
+CREATE OR REPLACE FUNCTION trigger_metadata_sync()
+    RETURNS void
+    LANGUAGE C STRICT
+    AS 'citus';
+CREATE OR REPLACE FUNCTION raise_error_in_metadata_sync()
+    RETURNS void
+    LANGUAGE C STRICT
+    AS 'citus';
+CREATE PROCEDURE wait_until_process_count(appname text, target_count int) AS $$
+declare
+   counter integer := -1;
+begin
+ while counter != target_count loop
+  -- pg_stat_activity is cached at xact level and there is no easy way to clear it.
+  -- Look it up in a new connection to get latest updates.
+  SELECT result::int into counter FROM
+   master_run_on_worker(ARRAY['localhost'], ARRAY[57636], ARRAY[
+      'SELECT count(*) FROM pg_stat_activity WHERE application_name = ' || quote_literal(appname) || ';'], false);
+  PERFORM pg_sleep(0.1);
+ end loop;
+end$$ LANGUAGE plpgsql;
 -- add a node to the cluster
 SELECT master_add_node('localhost', :worker_1_port) As nodeid_1 \gset
 SELECT nodeid, nodename, nodeport, hasmetadata, metadatasynced FROM pg_dist_node;
@@ -152,6 +173,142 @@ SELECT nodeid, hasmetadata, metadatasynced FROM pg_dist_node;
       2 | t           | f
 (1 row)
 
+-- verify that metadata sync daemon has started
+SELECT count(*) FROM pg_stat_activity WHERE application_name = 'Citus Metadata Sync Daemon';
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+--
+-- terminate maintenance daemon, and verify that we don't spawn multiple
+-- metadata sync daemons
+--
+SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE application_name = 'Citus Maintenance Daemon';
+ pg_terminate_backend
+---------------------------------------------------------------------
+ t
+(1 row)
+
+CALL wait_until_process_count('Citus Maintenance Daemon', 1);
+select trigger_metadata_sync();
+ trigger_metadata_sync
+---------------------------------------------------------------------
+
+(1 row)
+
+select wait_until_metadata_sync();
+ wait_until_metadata_sync
+---------------------------------------------------------------------
+
+(1 row)
+
+SELECT count(*) FROM pg_stat_activity WHERE application_name = 'Citus Metadata Sync Daemon';
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+--
+-- cancel metadata sync daemon, and verify that it exits and restarts.
+--
+select pid as pid_before_cancel from pg_stat_activity where application_name like 'Citus Met%' \gset
+select pg_cancel_backend(pid) from pg_stat_activity where application_name = 'Citus Metadata Sync Daemon';
+ pg_cancel_backend
+---------------------------------------------------------------------
+ t
+(1 row)
+
+select wait_until_metadata_sync();
+ wait_until_metadata_sync
+---------------------------------------------------------------------
+
+(1 row)
+
+select pid as pid_after_cancel from pg_stat_activity where application_name like 'Citus Met%' \gset
+select :pid_before_cancel != :pid_after_cancel AS metadata_sync_restarted;
+ metadata_sync_restarted
+---------------------------------------------------------------------
+ t
+(1 row)
+
+--
+-- cancel metadata sync daemon so it exits and restarts, but at the
+-- same time tell maintenanced to trigger a new metadata sync. One
+-- of these should exit to avoid multiple metadata syncs.
+--
+select pg_cancel_backend(pid) from pg_stat_activity where application_name = 'Citus Metadata Sync Daemon';
+ pg_cancel_backend
+---------------------------------------------------------------------
+ t
+(1 row)
+
+select trigger_metadata_sync();
+ trigger_metadata_sync
+---------------------------------------------------------------------
+
+(1 row)
+
+select wait_until_metadata_sync();
+ wait_until_metadata_sync
+---------------------------------------------------------------------
+
+(1 row)
+
+-- we assume citus.metadata_sync_retry_interval is 500ms. Change amount we sleep to ceiling + 0.2 if it changes.
+select pg_sleep(1.2);
+ pg_sleep
+---------------------------------------------------------------------
+
+(1 row)
+
+SELECT count(*) FROM pg_stat_activity WHERE application_name = 'Citus Metadata Sync Daemon';
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+--
+-- error in metadata sync daemon, and verify it exits and restarts.
+--
+select pid as pid_before_error from pg_stat_activity where application_name like 'Citus Met%' \gset
+select raise_error_in_metadata_sync();
+ raise_error_in_metadata_sync
+---------------------------------------------------------------------
+
+(1 row)
+
+select wait_until_metadata_sync(30000);
+ wait_until_metadata_sync
+---------------------------------------------------------------------
+
+(1 row)
+
+select pid as pid_after_error from pg_stat_activity where application_name like 'Citus Met%' \gset
+select :pid_before_error != :pid_after_error AS metadata_sync_restarted;
+ metadata_sync_restarted
+---------------------------------------------------------------------
+ t
+(1 row)
+
+SELECT trigger_metadata_sync();
+ trigger_metadata_sync
+---------------------------------------------------------------------
+
+(1 row)
+
+SELECT wait_until_metadata_sync(30000);
+ wait_until_metadata_sync
+---------------------------------------------------------------------
+
+(1 row)
+
+SELECT count(*) FROM pg_stat_activity WHERE application_name = 'Citus Metadata Sync Daemon';
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
 -- update it back to :worker_1_port, now metadata should be synced
 SELECT 1 FROM master_update_node(:nodeid_1, 'localhost', :worker_1_port);
  ?column?
@@ -594,6 +751,59 @@ SELECT verify_metadata('localhost', :worker_1_port);
  t
 (1 row)
 
+-- verify that metadata sync daemon exits
+call wait_until_process_count('Citus Metadata Sync Daemon', 0);
+-- verify that DROP DATABASE terminates metadata sync
+SELECT current_database() datname \gset
+CREATE DATABASE db_to_drop;
+NOTICE:  Citus partially supports CREATE DATABASE for distributed databases
+SELECT run_command_on_workers('CREATE DATABASE db_to_drop');
+        run_command_on_workers
+---------------------------------------------------------------------
+ (localhost,57637,t,"CREATE DATABASE")
+ (localhost,57638,t,"CREATE DATABASE")
+(2 rows)
+
+\c db_to_drop - - :worker_1_port
+CREATE EXTENSION citus;
+\c db_to_drop - - :master_port
+CREATE EXTENSION citus;
+SELECT master_add_node('localhost', :worker_1_port);
+ master_add_node
+---------------------------------------------------------------------
+               1
+(1 row)
+
+UPDATE pg_dist_node SET hasmetadata = true;
+SELECT master_update_node(nodeid, 'localhost', 12345) FROM pg_dist_node;
+ master_update_node
+---------------------------------------------------------------------
+
+(1 row)
+
+CREATE OR REPLACE FUNCTION trigger_metadata_sync()
+    RETURNS void
+    LANGUAGE C STRICT
+    AS 'citus';
+SELECT trigger_metadata_sync();
+ trigger_metadata_sync
+---------------------------------------------------------------------
+
+(1 row)
+
+\c :datname - - :master_port
+SELECT datname FROM pg_stat_activity WHERE application_name LIKE 'Citus Met%';
+  datname
+---------------------------------------------------------------------
+ db_to_drop
+(1 row)
+
+DROP DATABASE db_to_drop;
+SELECT datname FROM pg_stat_activity WHERE application_name LIKE 'Citus Met%';
+ datname
+---------------------------------------------------------------------
+(0 rows)
+
 -- cleanup
 DROP TABLE ref_table;
 TRUNCATE pg_dist_colocation;

src/test/regress/expected/multi_prune_shard_list.out

@@ -84,7 +84,7 @@ SELECT prune_using_both_values('pruning', 'tomato', 'rose');
 
 -- unit test of the equality expression generation code
 SELECT debug_equality_expression('pruning');
-                                                                                                                                                                           debug_equality_expression
+                                                                                                                                                                            debug_equality_expression
 ---------------------------------------------------------------------
  {OPEXPR :opno 98 :opfuncid 67 :opresulttype 16 :opretset false :opcollid 0 :inputcollid 100 :args ({VAR :varno 1 :varattno 1 :vartype 25 :vartypmod -1 :varcollid 100 :varlevelsup 0 :varnoold 1 :varoattno 1 :location -1} {CONST :consttype 25 :consttypmod -1 :constcollid 100 :constlen -1 :constbyval false :constisnull true :location -1 :constvalue <>}) :location -1}
 (1 row)
@@ -543,6 +543,154 @@ SELECT * FROM numeric_test WHERE id = 21.1::numeric;
  21.1 |  87
 (1 row)
 
+CREATE TABLE range_dist_table_1 (dist_col BIGINT);
+SELECT create_distributed_table('range_dist_table_1', 'dist_col', 'range');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+CALL public.create_range_partitioned_shards('range_dist_table_1', '{1000,3000,6000}', '{2000,4000,7000}');
+INSERT INTO range_dist_table_1 VALUES (1001);
+INSERT INTO range_dist_table_1 VALUES (3800);
+INSERT INTO range_dist_table_1 VALUES (6500);
+-- all were returning false before fixing #5077
+SELECT SUM(dist_col)=3800+6500 FROM range_dist_table_1 WHERE dist_col >= 2999;
+ ?column?
+---------------------------------------------------------------------
+ t
+(1 row)
+
+SELECT SUM(dist_col)=3800+6500 FROM range_dist_table_1 WHERE dist_col > 2999;
+ ?column?
+---------------------------------------------------------------------
+ t
+(1 row)
+
+SELECT SUM(dist_col)=3800+6500 FROM range_dist_table_1 WHERE dist_col >= 2500;
+ ?column?
+---------------------------------------------------------------------
+ t
+(1 row)
+
+SELECT SUM(dist_col)=3800+6500 FROM range_dist_table_1 WHERE dist_col > 2000;
+ ?column?
+---------------------------------------------------------------------
+ t
+(1 row)
+
+SELECT SUM(dist_col)=3800+6500 FROM range_dist_table_1 WHERE dist_col > 1001;
+ ?column?
+---------------------------------------------------------------------
+ t
+(1 row)
+
+SELECT SUM(dist_col)=1001+3800+6500 FROM range_dist_table_1 WHERE dist_col >= 1001;
+ ?column?
+---------------------------------------------------------------------
+ t
+(1 row)
+
+SELECT SUM(dist_col)=1001+3800+6500 FROM range_dist_table_1 WHERE dist_col > 1000;
+ ?column?
+---------------------------------------------------------------------
+ t
+(1 row)
+
+SELECT SUM(dist_col)=1001+3800+6500 FROM range_dist_table_1 WHERE dist_col >= 1000;
+ ?column?
+---------------------------------------------------------------------
+ t
+(1 row)
+
+-- we didn't have such an off-by-one error in upper bound
+-- calculation, but let's test such cases too
+SELECT SUM(dist_col)=1001+3800 FROM range_dist_table_1 WHERE dist_col <= 4001;
+ ?column?
+---------------------------------------------------------------------
+ t
+(1 row)
+
+SELECT SUM(dist_col)=1001+3800 FROM range_dist_table_1 WHERE dist_col < 4001;
+ ?column?
+---------------------------------------------------------------------
+ t
+(1 row)
+
+SELECT SUM(dist_col)=1001+3800 FROM range_dist_table_1 WHERE dist_col <= 4500;
+ ?column?
+---------------------------------------------------------------------
+ t
+(1 row)
+
+SELECT SUM(dist_col)=1001+3800 FROM range_dist_table_1 WHERE dist_col < 6000;
+ ?column?
+---------------------------------------------------------------------
+ t
+(1 row)
+
+-- now test with composite type and more shards
+CREATE TYPE comp_type AS (
+    int_field_1 BIGINT,
+    int_field_2 BIGINT
+);
+CREATE TYPE comp_type_range AS RANGE (
+    subtype = comp_type);
+CREATE TABLE range_dist_table_2 (dist_col comp_type);
+SELECT create_distributed_table('range_dist_table_2', 'dist_col', 'range');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+CALL public.create_range_partitioned_shards(
+	'range_dist_table_2',
+    '{"(10,24)","(10,58)",
+	  "(10,90)","(20,100)"}',
+	'{"(10,25)","(10,65)",
+	  "(10,99)","(20,100)"}');
+INSERT INTO range_dist_table_2 VALUES ((10, 24));
+INSERT INTO range_dist_table_2 VALUES ((10, 60));
+INSERT INTO range_dist_table_2 VALUES ((10, 91));
+INSERT INTO range_dist_table_2 VALUES ((20, 100));
+SELECT dist_col='(10, 60)'::comp_type FROM range_dist_table_2
+WHERE dist_col >= '(10,26)'::comp_type AND
+      dist_col <= '(10,75)'::comp_type;
+ ?column?
+---------------------------------------------------------------------
+ t
+(1 row)
+
+SELECT * FROM range_dist_table_2
+WHERE dist_col >= '(10,57)'::comp_type AND
+      dist_col <= '(10,95)'::comp_type
+ORDER BY dist_col;
+ dist_col
+---------------------------------------------------------------------
+ (10,60)
+ (10,91)
+(2 rows)
+
+SELECT * FROM range_dist_table_2
+WHERE dist_col >= '(10,57)'::comp_type
+ORDER BY dist_col;
+ dist_col
+---------------------------------------------------------------------
+ (10,60)
+ (10,91)
+ (20,100)
+(3 rows)
+
+SELECT dist_col='(20,100)'::comp_type FROM range_dist_table_2
+WHERE dist_col > '(20,99)'::comp_type;
+ ?column?
+---------------------------------------------------------------------
+ t
+(1 row)
+
+DROP TABLE range_dist_table_1, range_dist_table_2;
+DROP TYPE comp_type CASCADE;
+NOTICE:  drop cascades to type comp_type_range
 SET search_path TO public;
 DROP SCHEMA prune_shard_list CASCADE;
 NOTICE:  drop cascades to 10 other objects

src/test/regress/expected/multi_test_helpers_superuser.out

@@ -26,7 +26,7 @@ WITH dist_node_summary AS (
                             ARRAY[dist_node_summary.query, dist_node_summary.query],
                             false)
 ), dist_placement_summary AS (
-    SELECT 'SELECT jsonb_agg(pg_dist_placement ORDER BY shardid) FROM pg_dist_placement)' AS query
+    SELECT 'SELECT jsonb_agg(pg_dist_placement ORDER BY shardid) FROM pg_dist_placement' AS query
 ), dist_placement_check AS (
     SELECT count(distinct result) = 1 AS matches
     FROM dist_placement_summary CROSS JOIN LATERAL

src/test/regress/expected/mx_coordinator_shouldhaveshards.out

@@ -0,0 +1,183 @@
+CREATE SCHEMA mx_coordinator_shouldhaveshards;
+SET search_path TO mx_coordinator_shouldhaveshards;
+SET citus.shard_replication_factor to 1;
+SET citus.replication_model TO streaming;
+SET client_min_messages TO WARNING;
+SELECT 1 FROM master_add_node('localhost', :master_port, groupid => 0);
+ ?column?
+---------------------------------------------------------------------
+        1
+(1 row)
+
+RESET client_min_messages;
+SELECT 1 FROM master_set_node_property('localhost', :master_port, 'shouldhaveshards', true);
+ ?column?
+---------------------------------------------------------------------
+        1
+(1 row)
+
+-- issue 4508 table_1 and table_2 are used to test some edge cases
+-- around intermediate result pruning
+CREATE TABLE table_1 (key int, value text);
+SELECT create_distributed_table('table_1', 'key', colocate_with := 'none');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+CREATE TABLE table_2 (key int, value text);
+SELECT create_distributed_table('table_2', 'key', colocate_with := 'none');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+INSERT INTO table_1    VALUES (1, '1'), (2, '2'), (3, '3'), (4, '4');
+INSERT INTO table_2    VALUES (1, '1'), (2, '2'), (3, '3'), (4, '4'), (5, '5'), (6, '6');
+set citus.log_intermediate_results TO ON;
+set client_min_messages to debug1;
+WITH a AS (SELECT * FROM table_1 ORDER BY 1,2 DESC LIMIT 1)
+SELECT count(*),
+key
+FROM a JOIN table_2 USING (key)
+GROUP BY key
+HAVING (max(table_2.value) >= (SELECT value FROM a));
+DEBUG:  generating subplan XXX_1 for CTE a: SELECT key, value FROM mx_coordinator_shouldhaveshards.table_1 ORDER BY key, value DESC LIMIT 1
+DEBUG:  push down of limit count: 1
+DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT count(*) AS count, a.key FROM ((SELECT intermediate_result.key, intermediate_result.value FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(key integer, value text)) a JOIN mx_coordinator_shouldhaveshards.table_2 USING (key)) GROUP BY a.key HAVING (max(table_2.value) OPERATOR(pg_catalog.>=) (SELECT a_1.value FROM (SELECT intermediate_result.key, intermediate_result.value FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(key integer, value text)) a_1))
+DEBUG:  Subplan XXX_1 will be written to local file
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+ count | key
+---------------------------------------------------------------------
+     1 |   1
+(1 row)
+
+WITH a AS (SELECT * FROM table_1 ORDER BY 1,2 DESC LIMIT 1)
+INSERT INTO table_1 SELECT count(*),
+key
+FROM a JOIN table_2 USING (key)
+GROUP BY key
+HAVING (max(table_2.value) >= (SELECT value FROM a));
+DEBUG:  Group by list without distribution column is not allowed  in distributed INSERT ... SELECT queries
+DEBUG:  generating subplan XXX_1 for CTE a: SELECT key, value FROM mx_coordinator_shouldhaveshards.table_1 ORDER BY key, value DESC LIMIT 1
+DEBUG:  push down of limit count: 1
+DEBUG:  generating subplan XXX_2 for subquery SELECT count(*) AS count, a.key FROM ((SELECT intermediate_result.key, intermediate_result.value FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(key integer, value text)) a JOIN mx_coordinator_shouldhaveshards.table_2 USING (key)) GROUP BY a.key HAVING (max(table_2.value) OPERATOR(pg_catalog.>=) (SELECT a_1.value FROM (SELECT intermediate_result.key, intermediate_result.value FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(key integer, value text)) a_1))
+DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT int4(count) AS key, (key)::text AS value FROM (SELECT intermediate_result.count, intermediate_result.key FROM read_intermediate_result('XXX_2'::text, 'binary'::citus_copy_format) intermediate_result(count bigint, key integer)) citus_insert_select_subquery
+DEBUG:  Collecting INSERT ... SELECT results on coordinator
+DEBUG:  Subplan XXX_1 will be written to local file
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+DEBUG:  Subplan XXX_2 will be written to local file
+WITH stats AS (
+  SELECT count(key) m FROM table_1
+),
+inserts AS (
+  INSERT INTO table_2
+  SELECT key, count(*)
+  FROM table_1
+  WHERE key >= (SELECT m FROM stats)
+  GROUP BY key
+  HAVING count(*) <= (SELECT m FROM stats)
+  LIMIT 1
+  RETURNING *
+) SELECT count(*) FROM inserts;
+DEBUG:  generating subplan XXX_1 for CTE stats: SELECT count(key) AS m FROM mx_coordinator_shouldhaveshards.table_1
+DEBUG:  generating subplan XXX_2 for CTE inserts: INSERT INTO mx_coordinator_shouldhaveshards.table_2 (key, value) SELECT key, count(*) AS count FROM mx_coordinator_shouldhaveshards.table_1 WHERE (key OPERATOR(pg_catalog.>=) (SELECT stats.m FROM (SELECT intermediate_result.m FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(m bigint)) stats)) GROUP BY key HAVING (count(*) OPERATOR(pg_catalog.<=) (SELECT stats.m FROM (SELECT intermediate_result.m FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(m bigint)) stats)) LIMIT 1 RETURNING table_2.key, table_2.value
+DEBUG:  LIMIT clauses are not allowed in distributed INSERT ... SELECT queries
+DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT count(*) AS count FROM (SELECT intermediate_result.key, intermediate_result.value FROM read_intermediate_result('XXX_2'::text, 'binary'::citus_copy_format) intermediate_result(key integer, value text)) inserts
+DEBUG:  Subplan XXX_1 will be written to local file
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+DEBUG:  Subplan XXX_2 will be written to local file
+DEBUG:  Collecting INSERT ... SELECT results on coordinator
+ count
+---------------------------------------------------------------------
+     0
+(1 row)
+
+\c - - - :worker_1_port
+SET search_path TO mx_coordinator_shouldhaveshards;
+set citus.log_intermediate_results TO ON;
+set client_min_messages to debug1;
+WITH a AS (SELECT * FROM table_1 ORDER BY 1,2 DESC LIMIT 1)
+SELECT count(*),
+key
+FROM a JOIN table_2 USING (key)
+GROUP BY key
+HAVING (max(table_2.value) >= (SELECT value FROM a));
+DEBUG:  generating subplan XXX_1 for CTE a: SELECT key, value FROM mx_coordinator_shouldhaveshards.table_1 ORDER BY key, value DESC LIMIT 1
+DEBUG:  push down of limit count: 1
+DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT count(*) AS count, a.key FROM ((SELECT intermediate_result.key, intermediate_result.value FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(key integer, value text)) a JOIN mx_coordinator_shouldhaveshards.table_2 USING (key)) GROUP BY a.key HAVING (max(table_2.value) OPERATOR(pg_catalog.>=) (SELECT a_1.value FROM (SELECT intermediate_result.key, intermediate_result.value FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(key integer, value text)) a_1))
+DEBUG:  Subplan XXX_1 will be written to local file
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+ count | key
+---------------------------------------------------------------------
+     1 |   1
+(1 row)
+
+WITH a AS (SELECT * FROM table_1 ORDER BY 1,2 DESC LIMIT 1)
+INSERT INTO table_1 SELECT count(*),
+key
+FROM a JOIN table_2 USING (key)
+GROUP BY key
+HAVING (max(table_2.value) >= (SELECT value FROM a));
+DEBUG:  Group by list without distribution column is not allowed  in distributed INSERT ... SELECT queries
+DEBUG:  generating subplan XXX_1 for CTE a: SELECT key, value FROM mx_coordinator_shouldhaveshards.table_1 ORDER BY key, value DESC LIMIT 1
+DEBUG:  push down of limit count: 1
+DEBUG:  generating subplan XXX_2 for subquery SELECT count(*) AS count, a.key FROM ((SELECT intermediate_result.key, intermediate_result.value FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(key integer, value text)) a JOIN mx_coordinator_shouldhaveshards.table_2 USING (key)) GROUP BY a.key HAVING (max(table_2.value) OPERATOR(pg_catalog.>=) (SELECT a_1.value FROM (SELECT intermediate_result.key, intermediate_result.value FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(key integer, value text)) a_1))
+DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT int4(count) AS key, (key)::text AS value FROM (SELECT intermediate_result.count, intermediate_result.key FROM read_intermediate_result('XXX_2'::text, 'binary'::citus_copy_format) intermediate_result(count bigint, key integer)) citus_insert_select_subquery
+DEBUG:  Collecting INSERT ... SELECT results on coordinator
+DEBUG:  Subplan XXX_1 will be written to local file
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+DEBUG:  Subplan XXX_2 will be written to local file
+WITH stats AS (
+  SELECT count(key) m FROM table_1
+),
+inserts AS (
+  INSERT INTO table_2
+  SELECT key, count(*)
+  FROM table_1
+  WHERE key >= (SELECT m FROM stats)
+  GROUP BY key
+  HAVING count(*) <= (SELECT m FROM stats)
+  LIMIT 1
+  RETURNING *
+) SELECT count(*) FROM inserts;
+DEBUG:  generating subplan XXX_1 for CTE stats: SELECT count(key) AS m FROM mx_coordinator_shouldhaveshards.table_1
+DEBUG:  generating subplan XXX_2 for CTE inserts: INSERT INTO mx_coordinator_shouldhaveshards.table_2 (key, value) SELECT key, count(*) AS count FROM mx_coordinator_shouldhaveshards.table_1 WHERE (key OPERATOR(pg_catalog.>=) (SELECT stats.m FROM (SELECT intermediate_result.m FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(m bigint)) stats)) GROUP BY key HAVING (count(*) OPERATOR(pg_catalog.<=) (SELECT stats.m FROM (SELECT intermediate_result.m FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(m bigint)) stats)) LIMIT 1 RETURNING table_2.key, table_2.value
+DEBUG:  LIMIT clauses are not allowed in distributed INSERT ... SELECT queries
+DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT count(*) AS count FROM (SELECT intermediate_result.key, intermediate_result.value FROM read_intermediate_result('XXX_2'::text, 'binary'::citus_copy_format) intermediate_result(key integer, value text)) inserts
+DEBUG:  Subplan XXX_1 will be written to local file
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+DEBUG:  Subplan XXX_1 will be sent to localhost:xxxxx
+DEBUG:  Subplan XXX_2 will be written to local file
+DEBUG:  Collecting INSERT ... SELECT results on coordinator
+ count
+---------------------------------------------------------------------
+     0
+(1 row)
+
+\c - - - :master_port
+SELECT 1 FROM master_set_node_property('localhost', :master_port, 'shouldhaveshards', false);
+ ?column?
+---------------------------------------------------------------------
+        1
+(1 row)
+
+DROP SCHEMA mx_coordinator_shouldhaveshards CASCADE;
+NOTICE:  drop cascades to 6 other objects
+DETAIL:  drop cascades to table mx_coordinator_shouldhaveshards.table_1
+drop cascades to table mx_coordinator_shouldhaveshards.table_1_1130052
+drop cascades to table mx_coordinator_shouldhaveshards.table_1_1130055
+drop cascades to table mx_coordinator_shouldhaveshards.table_2
+drop cascades to table mx_coordinator_shouldhaveshards.table_2_1130056
+drop cascades to table mx_coordinator_shouldhaveshards.table_2_1130059
+SELECT master_remove_node('localhost', :master_port);
+ master_remove_node
+---------------------------------------------------------------------
+
+(1 row)
+

src/test/regress/expected/shared_connection_stats.out

@@ -226,10 +226,11 @@ COMMIT;
 -- now, some of the optional connections would be skipped,
 -- and only 5 connections are used per node
 BEGIN;
-	SELECT count(*), pg_sleep(0.1) FROM test;
- count | pg_sleep
+	SET LOCAL citus.max_adaptive_executor_pool_size TO 16;
+	with cte_1 as (select pg_sleep(0.1) is null, a from test) SELECT a from cte_1 ORDER By 1 LIMIT 1;
+ a
 ---------------------------------------------------------------------
-   101 |
+ 0
 (1 row)
 
 	SELECT
@@ -493,7 +494,7 @@ BEGIN;
 (2 rows)
 
 ROLLBACK;
--- INSERT SELECT with RETURNING/ON CONFLICT clauses should honor shared_pool_size
+-- INSERT SELECT with RETURNING/ON CONFLICT clauses does not honor shared_pool_size
 -- in underlying COPY commands
 BEGIN;
 	SELECT pg_sleep(0.1);
@@ -502,7 +503,9 @@ BEGIN;
 
 (1 row)
 
-	INSERT INTO test SELECT i FROM generate_series(0,10) i RETURNING *;
+	-- make sure that we hit at least 4 shards per node, where 20 rows
+	-- is enough
+	INSERT INTO test SELECT i FROM generate_series(0,20) i RETURNING *;
  a
 ---------------------------------------------------------------------
   0
@@ -516,10 +519,20 @@ BEGIN;
   8
   9
  10
-(11 rows)
+ 11
+ 12
+ 13
+ 14
+ 15
+ 16
+ 17
+ 18
+ 19
+ 20
+(21 rows)
 
 	SELECT
-		connection_count_to_node
+		connection_count_to_node > current_setting('citus.max_shared_pool_size')::int
 	FROM
 		citus_remote_connection_stats()
 	WHERE
@@ -527,10 +540,10 @@ BEGIN;
 		database_name = 'regression'
 	ORDER BY
 		hostname, port;
- connection_count_to_node
+ ?column?
 ---------------------------------------------------------------------
-                        3
-                        3
+ t
+ t
 (2 rows)
 
 ROLLBACK;

src/test/regress/expected/single_node.out

@@ -100,6 +100,143 @@ WITH cte_1 AS (UPDATE test SET y = y - 1 RETURNING *) SELECT * FROM cte_1 ORDER
  5 | 6
 (5 rows)
 
+-- Test upsert with constraint
+CREATE TABLE upsert_test
+(
+	part_key int UNIQUE,
+	other_col int,
+	third_col int
+);
+-- distribute the table
+SELECT create_distributed_table('upsert_test', 'part_key');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- do a regular insert
+INSERT INTO upsert_test (part_key, other_col) VALUES (1, 1), (2, 2) RETURNING *;
+ part_key | other_col | third_col
+---------------------------------------------------------------------
+        1 |         1 |
+        2 |         2 |
+(2 rows)
+
+SET citus.log_remote_commands to true;
+-- observe that there is a conflict and the following query does nothing
+INSERT INTO upsert_test (part_key, other_col) VALUES (1, 1) ON CONFLICT DO NOTHING RETURNING *;
+NOTICE:  executing the command locally: INSERT INTO single_node.upsert_test_90630513 AS citus_table_alias (part_key, other_col) VALUES (1, 1) ON CONFLICT DO NOTHING RETURNING part_key, other_col, third_col
+ part_key | other_col | third_col
+---------------------------------------------------------------------
+(0 rows)
+
+-- same as the above with different syntax
+INSERT INTO upsert_test (part_key, other_col) VALUES (1, 1) ON CONFLICT (part_key) DO NOTHING RETURNING *;
+NOTICE:  executing the command locally: INSERT INTO single_node.upsert_test_90630513 AS citus_table_alias (part_key, other_col) VALUES (1, 1) ON CONFLICT(part_key) DO NOTHING RETURNING part_key, other_col, third_col
+ part_key | other_col | third_col
+---------------------------------------------------------------------
+(0 rows)
+
+-- again the same query with another syntax
+INSERT INTO upsert_test (part_key, other_col) VALUES (1, 1) ON CONFLICT ON CONSTRAINT upsert_test_part_key_key DO NOTHING RETURNING *;
+NOTICE:  executing the command locally: INSERT INTO single_node.upsert_test_90630513 AS citus_table_alias (part_key, other_col) VALUES (1, 1) ON CONFLICT ON CONSTRAINT upsert_test_part_key_key_90630513 DO NOTHING RETURNING part_key, other_col, third_col
+ part_key | other_col | third_col
+---------------------------------------------------------------------
+(0 rows)
+
+BEGIN;
+-- force local execution
+SELECT count(*) FROM upsert_test WHERE part_key = 1;
+NOTICE:  executing the command locally: SELECT count(*) AS count FROM single_node.upsert_test_90630513 upsert_test WHERE (part_key OPERATOR(pg_catalog.=) 1)
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+SET citus.log_remote_commands to false;
+-- multi-shard pushdown query that goes through local execution
+INSERT INTO upsert_test (part_key, other_col) SELECT part_key, other_col FROM upsert_test ON CONFLICT ON CONSTRAINT upsert_test_part_key_key DO NOTHING RETURNING *;
+ part_key | other_col | third_col
+---------------------------------------------------------------------
+(0 rows)
+
+-- multi-shard pull-to-coordinator query that goes through local execution
+INSERT INTO upsert_test (part_key, other_col) SELECT part_key, other_col FROM upsert_test LIMIT 100 ON CONFLICT ON CONSTRAINT upsert_test_part_key_key DO NOTHING RETURNING *;
+ part_key | other_col | third_col
+---------------------------------------------------------------------
+(0 rows)
+
+COMMIT;
+-- to test citus local tables
+select undistribute_table('upsert_test');
+NOTICE:  creating a new local table for single_node.upsert_test
+NOTICE:  Moving the data of single_node.upsert_test
+NOTICE:  Dropping the old single_node.upsert_test
+NOTICE:  Renaming the new table to single_node.upsert_test
+ undistribute_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- create citus local table
+select create_citus_local_table('upsert_test');
+ create_citus_local_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- test the constraint with local execution
+INSERT INTO upsert_test (part_key, other_col) VALUES (1, 1) ON CONFLICT ON CONSTRAINT upsert_test_part_key_key DO NOTHING RETURNING *;
+ part_key | other_col | third_col
+---------------------------------------------------------------------
+(0 rows)
+
+DROP TABLE upsert_test;
+CREATE SCHEMA "Quoed.Schema";
+SET search_path TO "Quoed.Schema";
+CREATE TABLE "long_constraint_upsert\_test"
+(
+	part_key int,
+	other_col int,
+	third_col int,
+	CONSTRAINT "looo oooo ooooo ooooooooooooooooo oooooooo oooooooo ng quoted  \aconstraint" UNIQUE (part_key)
+);
+NOTICE:  identifier "looo oooo ooooo ooooooooooooooooo oooooooo oooooooo ng quoted  \aconstraint" will be truncated to "looo oooo ooooo ooooooooooooooooo oooooooo oooooooo ng quoted  "
+-- distribute the table and create shards
+SELECT create_distributed_table('"long_constraint_upsert\_test"', 'part_key');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+INSERT INTO "long_constraint_upsert\_test" (part_key, other_col) VALUES (1, 1) ON CONFLICT ON CONSTRAINT  "looo oooo ooooo ooooooooooooooooo oooooooo oooooooo ng quoted  \aconstraint" DO NOTHING RETURNING *;
+NOTICE:  identifier "looo oooo ooooo ooooooooooooooooo oooooooo oooooooo ng quoted  \aconstraint" will be truncated to "looo oooo ooooo ooooooooooooooooo oooooooo oooooooo ng quoted  "
+ part_key | other_col | third_col
+---------------------------------------------------------------------
+        1 |         1 |
+(1 row)
+
+ALTER TABLE "long_constraint_upsert\_test" RENAME TO simple_table_name;
+INSERT INTO simple_table_name (part_key, other_col) VALUES (1, 1) ON CONFLICT ON CONSTRAINT  "looo oooo ooooo ooooooooooooooooo oooooooo oooooooo ng quoted  \aconstraint" DO NOTHING RETURNING *;
+NOTICE:  identifier "looo oooo ooooo ooooooooooooooooo oooooooo oooooooo ng quoted  \aconstraint" will be truncated to "looo oooo ooooo ooooooooooooooooo oooooooo oooooooo ng quoted  "
+ part_key | other_col | third_col
+---------------------------------------------------------------------
+(0 rows)
+
+-- this is currently not supported, but once we support
+-- make sure that the following query also works fine
+ALTER TABLE simple_table_name RENAME CONSTRAINT "looo oooo ooooo ooooooooooooooooo oooooooo oooooooo ng quoted  \aconstraint"  TO simple_constraint_name;
+NOTICE:  identifier "looo oooo ooooo ooooooooooooooooo oooooooo oooooooo ng quoted  \aconstraint" will be truncated to "looo oooo ooooo ooooooooooooooooo oooooooo oooooooo ng quoted  "
+ERROR:  renaming constraints belonging to distributed tables is currently unsupported
+--INSERT INTO simple_table_name (part_key, other_col) VALUES (1, 1) ON CONFLICT ON CONSTRAINT  simple_constraint_name DO NOTHING RETURNING *;
+SET search_path TO single_node;
+DROP SCHEMA  "Quoed.Schema" CASCADE;
+NOTICE:  drop cascades to 5 other objects
+DETAIL:  drop cascades to table "Quoed.Schema".simple_table_name
+drop cascades to table "Quoed.Schema".simple_table_name_90630518
+drop cascades to table "Quoed.Schema".simple_table_name_90630519
+drop cascades to table "Quoed.Schema".simple_table_name_90630520
+drop cascades to table "Quoed.Schema".simple_table_name_90630521
 -- we should be able to limit intermediate results
 BEGIN;
        SET LOCAL citus.max_intermediate_result_size TO 0;

src/test/regress/expected/subquery_prepared_statements.out

@@ -119,16 +119,6 @@ EXECUTE subquery_prepare_without_param;
  (5,4)
 (5 rows)
 
-EXECUTE subquery_prepare_without_param;
- values_of_subquery
----------------------------------------------------------------------
- (6,4)
- (6,3)
- (6,2)
- (6,1)
- (5,4)
-(5 rows)
-
 EXECUTE subquery_prepare_param_on_partkey(1);
 DEBUG:  push down of limit count: 5
 DEBUG:  generating subplan XXX_1 for subquery SELECT DISTINCT ROW(users_table.user_id, events_table.event_type)::subquery_prepared_statements.xy AS values_of_subquery FROM public.users_table, public.events_table WHERE ((users_table.user_id OPERATOR(pg_catalog.=) events_table.user_id) AND ((users_table.user_id OPERATOR(pg_catalog.=) 1) OR (users_table.user_id OPERATOR(pg_catalog.=) 2)) AND (events_table.event_type OPERATOR(pg_catalog.=) ANY (ARRAY[1, 2, 3, 4]))) ORDER BY ROW(users_table.user_id, events_table.event_type)::subquery_prepared_statements.xy DESC LIMIT 5