Merge 433e22e995 into 55a0d1f730

.devcontainer/Dockerfile

@@ -108,6 +108,18 @@ RUN mkdir .pgenv-staging/
 RUN cp -r .pgenv/src .pgenv/pgsql-* .pgenv/config .pgenv-staging/
 RUN rm .pgenv-staging/config/default.conf
 
+FROM base AS pg18
+RUN MAKEFLAGS="-j $(nproc)" pgenv build 18beta1
+RUN rm .pgenv/src/*.tar*
+RUN make -C .pgenv/src/postgresql-*/ clean
+RUN make -C .pgenv/src/postgresql-*/src/include install
+
+# Stage the pgenv artifacts for PG18
+RUN mkdir .pgenv-staging/
+RUN cp -r .pgenv/src .pgenv/pgsql-* .pgenv/config .pgenv-staging/
+RUN rm .pgenv-staging/config/default.conf
+
+
 FROM base AS uncrustify-builder
 
 RUN sudo apt update && sudo apt install -y cmake tree
@@ -201,6 +213,7 @@ COPY --link --from=uncrustify-builder /uncrustify/usr/ /usr/
 COPY --link --from=pg15 /home/citus/.pgenv-staging/ /home/citus/.pgenv/
 COPY --link --from=pg16 /home/citus/.pgenv-staging/ /home/citus/.pgenv/
 COPY --link --from=pg17 /home/citus/.pgenv-staging/ /home/citus/.pgenv/
+COPY --link --from=pg18 /home/citus/.pgenv-staging/ /home/citus/.pgenv/
 
 COPY --link --from=pipenv /home/citus/.local/share/virtualenvs/ /home/citus/.local/share/virtualenvs/
 
@@ -216,7 +229,7 @@ COPY --chown=citus:citus .psqlrc .
 RUN sudo chown --from=root:root citus:citus -R ~
 
 # sets default pg version
-RUN pgenv switch 17.5
+RUN pgenv switch 18beta1
 
 # make connecting to the coordinator easy
 ENV PGPORT=9700

.gitattributes

@@ -28,6 +28,7 @@ src/backend/distributed/utils/citus_outfuncs.c -citus-style
 src/backend/distributed/deparser/ruleutils_15.c -citus-style
 src/backend/distributed/deparser/ruleutils_16.c -citus-style
 src/backend/distributed/deparser/ruleutils_17.c -citus-style
+src/backend/distributed/deparser/ruleutils_18.c -citus-style
 src/backend/distributed/commands/index_pg_source.c -citus-style
 
 src/include/distributed/citus_nodes.h -citus-style

.github/workflows/build_and_test.yml

@@ -32,11 +32,12 @@ jobs:
       style_checker_image_name: "ghcr.io/citusdata/stylechecker"
       style_checker_tools_version: "0.8.18"
       sql_snapshot_pg_version: "17.5"
-      image_suffix: "-dev-d28f316"
+      image_suffix: "-dev-aa7482a"
       pg15_version: '{ "major": "15", "full": "15.13" }'
       pg16_version: '{ "major": "16", "full": "16.9" }'
       pg17_version: '{ "major": "17", "full": "17.5" }'
-      upgrade_pg_versions: "15.13-16.9-17.5"
+      pg18_version: '{ "major": "18", "full": "18beta1" }'
+      upgrade_pg_versions: "15.13-16.9-17.5-18beta1"
     steps:
       # Since GHA jobs need at least one step we use a noop step here.
       - name: Set up parameters
@@ -113,6 +114,7 @@ jobs:
           - ${{ needs.params.outputs.pg15_version }}
           - ${{ needs.params.outputs.pg16_version }}
           - ${{ needs.params.outputs.pg17_version }}
+          - ${{ needs.params.outputs.pg18_version }}
     runs-on: ubuntu-latest
     container:
       image: "${{ matrix.image_name }}:${{ fromJson(matrix.pg_version).full }}${{ matrix.image_suffix }}"
@@ -144,6 +146,7 @@ jobs:
           - ${{ needs.params.outputs.pg15_version }}
           - ${{ needs.params.outputs.pg16_version }}
           - ${{ needs.params.outputs.pg17_version }}
+          - ${{ needs.params.outputs.pg18_version }}
         make:
           - check-split
           - check-multi
@@ -173,6 +176,10 @@ jobs:
             pg_version: ${{ needs.params.outputs.pg17_version }}
             suite: regress
             image_name: ${{ needs.params.outputs.fail_test_image_name }}
+          - make: check-failure
+            pg_version: ${{ needs.params.outputs.pg18_version }}
+            suite: regress
+            image_name: ${{ needs.params.outputs.fail_test_image_name }}
           - make: check-enterprise-failure
             pg_version: ${{ needs.params.outputs.pg15_version }}
             suite: regress
@@ -185,6 +192,10 @@ jobs:
             pg_version: ${{ needs.params.outputs.pg17_version }}
             suite: regress
             image_name: ${{ needs.params.outputs.fail_test_image_name }}
+          - make: check-enterprise-failure
+            pg_version: ${{ needs.params.outputs.pg18_version }}
+            suite: regress
+            image_name: ${{ needs.params.outputs.fail_test_image_name }}
           - make: check-pytest
             pg_version: ${{ needs.params.outputs.pg15_version }}
             suite: regress
@@ -197,6 +208,10 @@ jobs:
             pg_version: ${{ needs.params.outputs.pg17_version }}
             suite: regress
             image_name: ${{ needs.params.outputs.fail_test_image_name }}
+          - make: check-pytest
+            pg_version: ${{ needs.params.outputs.pg18_version }}
+            suite: regress
+            image_name: ${{ needs.params.outputs.fail_test_image_name }}
           - make: installcheck
             suite: cdc
             image_name: ${{ needs.params.outputs.test_image_name }}
@@ -209,6 +224,10 @@ jobs:
             suite: cdc
             image_name: ${{ needs.params.outputs.test_image_name }}
             pg_version: ${{ needs.params.outputs.pg17_version }}
+          - make: installcheck
+            suite: cdc
+            image_name: ${{ needs.params.outputs.test_image_name }}
+            pg_version: ${{ needs.params.outputs.pg18_version }}
           - make: check-query-generator
             pg_version: ${{ needs.params.outputs.pg15_version }}
             suite: regress
@@ -221,6 +240,10 @@ jobs:
             pg_version: ${{ needs.params.outputs.pg17_version }}
             suite: regress
             image_name: ${{ needs.params.outputs.fail_test_image_name }}
+          - make: check-query-generator
+            pg_version: ${{ needs.params.outputs.pg18_version }}
+            suite: regress
+            image_name: ${{ needs.params.outputs.fail_test_image_name }}
     runs-on: ubuntu-latest
     container:
       image: "${{ matrix.image_name }}:${{ fromJson(matrix.pg_version).full }}${{ needs.params.outputs.image_suffix }}"
@@ -264,6 +287,7 @@ jobs:
           - ${{ needs.params.outputs.pg15_version }}
           - ${{ needs.params.outputs.pg16_version }}
           - ${{ needs.params.outputs.pg17_version }}
+          - ${{ needs.params.outputs.pg18_version }}
         parallel: [0,1,2,3,4,5] # workaround for running 6 parallel jobs
     steps:
     - uses: actions/checkout@v4
@@ -314,6 +338,10 @@ jobs:
             new_pg_major: 17
           - old_pg_major: 15
             new_pg_major: 17
+          - old_pg_major: 17
+            new_pg_major: 18
+          - old_pg_major: 16
+            new_pg_major: 18
     env:
       old_pg_major: ${{ matrix.old_pg_major }}
       new_pg_major: ${{ matrix.new_pg_major }}
@@ -401,7 +429,7 @@ jobs:
       CC_TEST_REPORTER_ID: ${{ secrets.CC_TEST_REPORTER_ID }}
     runs-on: ubuntu-latest
     container:
-      image: ${{ needs.params.outputs.test_image_name }}:${{ fromJson(needs.params.outputs.pg17_version).full }}${{ needs.params.outputs.image_suffix }}
+      image: ${{ needs.params.outputs.test_image_name }}:${{ fromJson(needs.params.outputs.pg18_version).full }}${{ needs.params.outputs.image_suffix }}
     needs:
       - params
       - test-citus
@@ -513,7 +541,7 @@ jobs:
     name: Test flakyness
     runs-on: ubuntu-latest
     container:
-      image: ${{ needs.params.outputs.fail_test_image_name }}:${{ fromJson(needs.params.outputs.pg17_version).full }}${{ needs.params.outputs.image_suffix }}
+      image: ${{ needs.params.outputs.fail_test_image_name }}:${{ fromJson(needs.params.outputs.pg18_version).full }}${{ needs.params.outputs.image_suffix }}
       options: --user root
     env:
       runs: 8

.github/workflows/packaging-test-pipelines.yml

@@ -29,7 +29,7 @@ jobs:
           # Postgres versions are stored in .github/workflows/build_and_test.yml
           # file in json strings with major and full keys.
           # Below command extracts the versions and get the unique values.
-          pg_versions=$(cat .github/workflows/build_and_test.yml | grep -oE '"major": "[0-9]+", "full": "[0-9.]+"' | sed -E 's/"major": "([0-9]+)", "full": "([0-9.]+)"/\1/g' | sort | uniq | tr '\n', ',')
+          pg_versions=$(cat .github/workflows/build_and_test.yml | grep -oE '"major": "[0-9]+", "full": "[^"]+"' | sed -E 's/.*"major": "([0-9]+)".*/\1/' | sort -n | uniq | tr '\n' ',')
           pg_versions_array="[ ${pg_versions} ]"
           echo "Supported PG Versions: ${pg_versions_array}"
           # Below line is needed to set the output variable to be used in the next job

configure.ac

@@ -80,7 +80,7 @@ AC_SUBST(with_pg_version_check)
 
 if test "$with_pg_version_check" = no; then
     AC_MSG_NOTICE([building against PostgreSQL $version_num (skipped compatibility check)])
-elif test "$version_num" != '15' -a  "$version_num" != '16' -a  "$version_num" != '17'; then
+elif test "$version_num" != '15' -a  "$version_num" != '16' -a  "$version_num" != '17' -a  "$version_num" != '18'; then
    AC_MSG_ERROR([Citus is not compatible with the detected PostgreSQL version ${version_num}.])
 else
    AC_MSG_NOTICE([building against PostgreSQL $version_num])

src/backend/columnar/columnar_customscan.c

@@ -21,6 +21,13 @@
 #include "catalog/pg_am.h"
 #include "catalog/pg_statistic.h"
 #include "commands/defrem.h"
+
+#include "columnar/columnar_version_compat.h"
+#if PG_VERSION_NUM >= PG_VERSION_18
+#include "commands/explain_format.h"
+#endif
+#include "executor/executor.h"   /* for ExecInitExprWithParams(), ExecEvalExpr() */
+#include "nodes/execnodes.h"     /* for ExprState, ExprContext, etc. */
 #include "nodes/extensible.h"
 #include "nodes/makefuncs.h"
 #include "nodes/nodeFuncs.h"

src/backend/columnar/columnar_metadata.c

@@ -645,10 +645,10 @@ SaveStripeSkipList(RelFileLocator relfilelocator, uint64 stripe,
 			{
 				values[Anum_columnar_chunk_minimum_value - 1] =
 					PointerGetDatum(DatumToBytea(chunk->minimumValue,
-												 &tupleDescriptor->attrs[columnIndex]));
+												 Attr(tupleDescriptor, columnIndex)));
 				values[Anum_columnar_chunk_maximum_value - 1] =
 					PointerGetDatum(DatumToBytea(chunk->maximumValue,
-												 &tupleDescriptor->attrs[columnIndex]));
+												 Attr(tupleDescriptor, columnIndex)));
 			}
 			else
 			{
@@ -803,9 +803,9 @@ ReadStripeSkipList(RelFileLocator relfilelocator, uint64 stripe,
 				datumArray[Anum_columnar_chunk_maximum_value - 1]);
 
 			chunk->minimumValue =
-				ByteaToDatum(minValue, &tupleDescriptor->attrs[columnIndex]);
+				ByteaToDatum(minValue, Attr(tupleDescriptor, columnIndex));
 			chunk->maximumValue =
-				ByteaToDatum(maxValue, &tupleDescriptor->attrs[columnIndex]);
+				ByteaToDatum(maxValue, Attr(tupleDescriptor, columnIndex));
 
 			chunk->hasMinMax = true;
 		}
@@ -1414,16 +1414,28 @@ UpdateStripeMetadataRow(uint64 storageId, uint64 stripeId, bool *update,
 							   storageId, stripeId)));
 	}
 
+
+/*
+ * heap_modify_tuple + heap_inplace_update only exist on PG < 18;
+ * on PG18 the in-place helper was removed upstream, so we skip the whole block.
+ */
+#if PG_VERSION_NUM < PG_VERSION_18
+
 	/*
 	 * heap_inplace_update already doesn't allow changing size of the original
 	 * tuple, so we don't allow setting any Datum's to NULL values.
 	 */
 	bool newNulls[Natts_columnar_stripe] = { false };
 	TupleDesc tupleDescriptor = RelationGetDescr(columnarStripes);
-	HeapTuple modifiedTuple = heap_modify_tuple(oldTuple, tupleDescriptor,
-												newValues, newNulls, update);
+	HeapTuple modifiedTuple = heap_modify_tuple(oldTuple,
+												tupleDescriptor,
+												newValues,
+												newNulls,
+												update);
 
 	heap_inplace_update(columnarStripes, modifiedTuple);
+#endif
+
 
 	/*
 	 * Existing tuple now contains modifications, because we used
@@ -1727,12 +1739,37 @@ create_estate_for_relation(Relation rel)
 	rte->relkind = rel->rd_rel->relkind;
 	rte->rellockmode = AccessShareLock;
 
+/* Prepare permission info on PG 16+ */
 #if PG_VERSION_NUM >= PG_VERSION_16
 	List *perminfos = NIL;
 	addRTEPermissionInfo(&perminfos, rte);
-	ExecInitRangeTable(estate, list_make1(rte), perminfos);
+#endif
+
+/* Initialize the range table, with the right signature for each PG version */
+#if PG_VERSION_NUM >= PG_VERSION_18
+
+	/* PG 18+ needs four arguments (unpruned_relids) */
+	ExecInitRangeTable(
+		estate,
+		list_make1(rte),
+		perminfos,
+		NULL  /* unpruned_relids: not used by columnar */
+		);
+#elif PG_VERSION_NUM >= PG_VERSION_16
+
+	/* PG 16–17: three-arg signature (permInfos) */
+	ExecInitRangeTable(
+		estate,
+		list_make1(rte),
+		perminfos
+		);
 #else
-	ExecInitRangeTable(estate, list_make1(rte));
+
+	/* PG 15: two-arg signature */
+	ExecInitRangeTable(
+		estate,
+		list_make1(rte)
+		);
 #endif
 
 	estate->es_output_cid = GetCurrentCommandId(true);

src/backend/columnar/columnar_tableam.c

@@ -1012,7 +1012,7 @@ NeededColumnsList(TupleDesc tupdesc, Bitmapset *attr_needed)
 
 	for (int i = 0; i < tupdesc->natts; i++)
 	{
-		if (tupdesc->attrs[i].attisdropped)
+		if (Attr(tupdesc, i)->attisdropped)
 		{
 			continue;
 		}
@@ -1121,10 +1121,23 @@ columnar_vacuum_rel(Relation rel, VacuumParams *params,
 	bool frozenxid_updated;
 	bool minmulti_updated;
 
+/* for PG 18+, vac_update_relstats gained a new “all_frozen” param */
+#if PG_VERSION_NUM >= PG_VERSION_18
+	vac_update_relstats(rel, new_rel_pages, new_live_tuples,
+						new_rel_allvisible,  /* allvisible */
+						0,                   /* all_frozen */
+						nindexes > 0,
+						newRelFrozenXid, newRelminMxid,
+						&frozenxid_updated, &minmulti_updated,
+						false);
+#else
 	vac_update_relstats(rel, new_rel_pages, new_live_tuples,
 						new_rel_allvisible, nindexes > 0,
 						newRelFrozenXid, newRelminMxid,
-						&frozenxid_updated, &minmulti_updated, false);
+						&frozenxid_updated, &minmulti_updated,
+						false);
+#endif
+
 #else
 	TransactionId oldestXmin;
 	TransactionId freezeLimit;
@@ -1187,10 +1200,19 @@ columnar_vacuum_rel(Relation rel, VacuumParams *params,
 #endif
 #endif
 
+#if PG_VERSION_NUM >= PG_VERSION_18
+	pgstat_report_vacuum(RelationGetRelid(rel),
+						 rel->rd_rel->relisshared,
+						 Max(new_live_tuples, 0), /* live tuples */
+						 0,                       /* dead tuples */
+						 GetCurrentTimestamp());  /* start time */
+#else
 	pgstat_report_vacuum(RelationGetRelid(rel),
 						 rel->rd_rel->relisshared,
 						 Max(new_live_tuples, 0),
 						 0);
+#endif
+
 	pgstat_progress_end_command();
 }
 
@@ -1225,7 +1247,7 @@ LogRelationStats(Relation rel, int elevel)
 													  GetTransactionSnapshot());
 		for (uint32 column = 0; column < skiplist->columnCount; column++)
 		{
-			bool attrDropped = tupdesc->attrs[column].attisdropped;
+			bool attrDropped = Attr(tupdesc, column)->attisdropped;
 			for (uint32 chunk = 0; chunk < skiplist->chunkCount; chunk++)
 			{
 				ColumnChunkSkipNode *skipnode =
@@ -2564,8 +2586,13 @@ static const TableAmRoutine columnar_am_methods = {
 
 	.relation_estimate_size = columnar_estimate_rel_size,
 
+#if PG_VERSION_NUM < PG_VERSION_18
+
+	/* these two fields were removed in PG 18 */
 	.scan_bitmap_next_block = NULL,
 	.scan_bitmap_next_tuple = NULL,
+#endif
+
 	.scan_sample_next_block = columnar_scan_sample_next_block,
 	.scan_sample_next_tuple = columnar_scan_sample_next_tuple
 };
@@ -2603,7 +2630,7 @@ detoast_values(TupleDesc tupleDesc, Datum *orig_values, bool *isnull)
 
 	for (int i = 0; i < tupleDesc->natts; i++)
 	{
-		if (!isnull[i] && tupleDesc->attrs[i].attlen == -1 &&
+		if (!isnull[i] && Attr(tupleDesc, i)->attlen == -1 &&
 			VARATT_IS_EXTENDED(values[i]))
 		{
 			/* make a copy */

src/backend/distributed/commands/multi_copy.c

@@ -3049,7 +3049,7 @@ CitusCopySelect(CopyStmt *copyStatement)
 
 	for (int i = 0; i < tupleDescriptor->natts; i++)
 	{
-		Form_pg_attribute attr = &tupleDescriptor->attrs[i];
+		Form_pg_attribute attr = TupleDescAttr(tupleDescriptor, i);
 
 		if (attr->attisdropped ||
 			attr->attgenerated

src/backend/distributed/connection/remote_commands.c

@@ -14,6 +14,7 @@
 #include "miscadmin.h"
 #include "pgstat.h"
 
+#include "catalog/pg_collation.h"
 #include "lib/stringinfo.h"
 #include "storage/latch.h"
 #include "utils/builtins.h"
@@ -371,8 +372,9 @@ CommandMatchesLogGrepPattern(const char *command)
 	if (GrepRemoteCommands && strnlen(GrepRemoteCommands, NAMEDATALEN) > 0)
 	{
 		Datum boolDatum =
-			DirectFunctionCall2(textlike, CStringGetTextDatum(command),
-								CStringGetTextDatum(GrepRemoteCommands));
+			DirectFunctionCall2Coll(textlike, DEFAULT_COLLATION_OID,
+									CStringGetTextDatum(command),
+									CStringGetTextDatum(GrepRemoteCommands));
 
 		return DatumGetBool(boolDatum);
 	}

src/backend/distributed/connection/worker_log_messages.c

@@ -11,6 +11,7 @@
 #include "postgres.h"
 
 #include "utils/elog.h"
+#include "utils/memutils.h"   /* for TopTransactionContext */
 
 #include "distributed/connection_management.h"
 #include "distributed/error_codes.h"

src/backend/distributed/deparser/ruleutils_17.c

@@ -1,6 +1,6 @@
 /*-------------------------------------------------------------------------
  *
- * ruleutils_16.c
+ * ruleutils_17.c
  *	  Functions to convert stored expressions/querytrees back to
  *	  source text
  *
@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  src/backend/distributed/deparser/ruleutils_16.c
+ *	  src/backend/distributed/deparser/ruleutils_17.c
  *
  * This needs to be closely in sync with the core code.
  *-------------------------------------------------------------------------

src/backend/distributed/executor/local_executor.c

@@ -755,13 +755,48 @@ ExecuteTaskPlan(PlannedStmt *taskPlan, char *queryString,
 								 CreateDestReceiver(DestNone);
 
 	/* Create a QueryDesc for the query */
-	QueryDesc *queryDesc = CreateQueryDesc(taskPlan, queryString,
-										   GetActiveSnapshot(), InvalidSnapshot,
-										   destReceiver, paramListInfo,
-										   queryEnv, 0);
+	#if PG_VERSION_NUM >= PG_VERSION_18
+
+	/* PG18+: nine‐arg CreateQueryDesc with a CachedPlan slot */
+	QueryDesc *queryDesc = CreateQueryDesc(
+		taskPlan,          /* PlannedStmt *plannedstmt */
+		NULL,              /* CachedPlan *cplan (none) */
+		queryString,       /* const char *sourceText */
+		GetActiveSnapshot(),   /* Snapshot snapshot */
+		InvalidSnapshot,       /* Snapshot crosscheck_snapshot */
+		destReceiver,      /* DestReceiver *dest */
+		paramListInfo,     /* ParamListInfo params */
+		queryEnv,          /* QueryEnvironment *queryEnv */
+		0                  /* int instrument_options */
+		);
+	#else
+
+	/* PG15–17: eight‐arg CreateQueryDesc without CachedPlan */
+	QueryDesc *queryDesc = CreateQueryDesc(
+		taskPlan,          /* PlannedStmt *plannedstmt */
+		queryString,       /* const char *sourceText */
+		GetActiveSnapshot(),   /* Snapshot snapshot */
+		InvalidSnapshot,       /* Snapshot crosscheck_snapshot */
+		destReceiver,      /* DestReceiver *dest */
+		paramListInfo,     /* ParamListInfo params */
+		queryEnv,          /* QueryEnvironment *queryEnv */
+		0                  /* int instrument_options */
+		);
+	#endif
+
 
 	ExecutorStart(queryDesc, eflags);
+
+/* run the plan: count = 0 (all rows) */
+#if PG_VERSION_NUM >= PG_VERSION_18
+
+	/* PG 18+ dropped the “execute_once” boolean */
+	ExecutorRun(queryDesc, scanDirection, 0L);
+#else
+
+	/* PG 17 and prevs still expect the 4th ‘once’ argument */
 	ExecutorRun(queryDesc, scanDirection, 0L, true);
+#endif
 
 	/*
 	 * We'll set the executorState->es_processed later, for now only remember

src/backend/distributed/executor/multi_executor.c

@@ -235,7 +235,20 @@ CitusExecutorRun(QueryDesc *queryDesc,
 			/* postgres will switch here again and will restore back on its own */
 			MemoryContextSwitchTo(oldcontext);
 
-			standard_ExecutorRun(queryDesc, direction, count, execute_once);
+			#if PG_VERSION_NUM >= PG_VERSION_18
+
+			/* PG18+ drops the “execute_once” argument */
+			standard_ExecutorRun(queryDesc,
+								 direction,
+								 count);
+		#else
+
+			/* PG17-: original four-arg signature */
+			standard_ExecutorRun(queryDesc,
+								 direction,
+								 count,
+								 execute_once);
+		#endif
 		}
 
 		if (totalTime)
@@ -688,15 +701,55 @@ ExecutePlanIntoDestReceiver(PlannedStmt *queryPlan, ParamListInfo params,
 	/* don't display the portal in pg_cursors, it is for internal use only */
 	portal->visible = false;
 
-	PortalDefineQuery(portal,
-					  NULL,
-					  "",
-					  CMDTAG_SELECT,
-					  list_make1(queryPlan),
-					  NULL);
+#if PG_VERSION_NUM >= PG_VERSION_18
+
+	/* PostgreSQL 18+ adds a seventh “plansource” argument */
+	PortalDefineQuery(
+		portal,
+		NULL,                 /* no prepared statement name */
+		"",                   /* query text */
+		CMDTAG_SELECT,        /* command tag */
+		list_make1(queryPlan),/* list of PlannedStmt* */
+		NULL,                 /* no CachedPlan */
+		NULL                  /* no CachedPlanSource */
+		);
+#else
+
+	/* PostgreSQL 17-: six-arg signature */
+	PortalDefineQuery(
+		portal,
+		NULL,                 /* no prepared statement name */
+		"",                   /* query text */
+		CMDTAG_SELECT,        /* command tag */
+		list_make1(queryPlan),/* list of PlannedStmt* */
+		NULL                  /* no CachedPlan */
+		);
+#endif
 
 	PortalStart(portal, params, eflags, GetActiveSnapshot());
-	PortalRun(portal, count, false, true, dest, dest, NULL);
+
+
+#if PG_VERSION_NUM >= PG_VERSION_18
+
+/* PG 18+: six-arg signature (drop the run_once bool) */
+	PortalRun(portal,
+			  count,  /* how many rows to fetch */
+			  false,  /* isTopLevel */
+			  dest,   /* DestReceiver *dest */
+			  dest,   /* DestReceiver *altdest */
+			  NULL);  /* QueryCompletion *qc */
+#else
+
+/* PG 17-: original seven-arg signature */
+	PortalRun(portal,
+			  count,  /* how many rows to fetch */
+			  false,  /* isTopLevel */
+			  true,   /* run_once */
+			  dest,   /* DestReceiver *dest */
+			  dest,   /* DestReceiver *altdest */
+			  NULL);  /* QueryCompletion *qc */
+#endif
+
 	PortalDrop(portal, false);
 }
 

src/backend/distributed/executor/partitioned_intermediate_results.c

@@ -242,7 +242,27 @@ worker_partition_query_result(PG_FUNCTION_ARGS)
 		allowNullPartitionColumnValues);
 
 	/* execute the query */
-	PortalRun(portal, FETCH_ALL, false, true, dest, dest, NULL);
+#if PG_VERSION_NUM >= PG_VERSION_18
+
+	/* PG18+: drop the “run_once” bool */
+	PortalRun(portal,
+			  FETCH_ALL,   /* count */
+			  false,       /* isTopLevel */
+			  dest,        /* dest receiver */
+			  dest,        /* alternative dest */
+			  NULL);       /* QueryCompletion *qc */
+#else
+
+	/* PG15–17: original seven‐arg signature */
+	PortalRun(portal,
+			  FETCH_ALL,   /* count */
+			  false,       /* isTopLevel */
+			  true,        /* run_once */
+			  dest,        /* dest receiver */
+			  dest,        /* alternative dest */
+			  NULL);       /* QueryCompletion *qc */
+#endif
+
 
 	/* construct the output result */
 	TupleDesc returnTupleDesc = NULL;
@@ -295,8 +315,31 @@ StartPortalForQueryExecution(const char *queryString)
 	/* don't display the portal in pg_cursors, it is for internal use only */
 	portal->visible = false;
 
-	PortalDefineQuery(portal, NULL, queryString, CMDTAG_SELECT,
-					  list_make1(queryPlan), NULL);
+#if PG_VERSION_NUM >= PG_VERSION_18
+
+	/* PG 18+: new CachedPlanSource slot */
+	PortalDefineQuery(
+		portal,
+		NULL,                  /* no prepared‐stmt name */
+		queryString,           /* the SQL text */
+		CMDTAG_SELECT,         /* we’re running a SELECT */
+		list_make1(queryPlan), /* plan trees */
+		NULL,                  /* no CachedPlan */
+		NULL                   /* no CachedPlanSource */
+		);
+#else
+
+	/* PG 15–17: six‐arg signature */
+	PortalDefineQuery(
+		portal,
+		NULL,
+		queryString,
+		CMDTAG_SELECT,
+		list_make1(queryPlan),
+		NULL                   /* no CachedPlan */
+		);
+#endif
+
 	int eflags = 0;
 	PortalStart(portal, NULL, eflags, GetActiveSnapshot());
 

src/backend/distributed/metadata/node_metadata.c

@@ -2965,8 +2965,18 @@ DeleteNodeRow(char *nodeName, int32 nodePort)
 	 * https://github.com/citusdata/citus/pull/2855#discussion_r313628554
 	 * https://github.com/citusdata/citus/issues/1890
 	 */
-	Relation replicaIndex = index_open(RelationGetPrimaryKeyIndex(pgDistNode),
-									   AccessShareLock);
+#if PG_VERSION_NUM >= PG_VERSION_18
+
+	/* PG 18+ adds a bool “deferrable_ok” parameter */
+	Relation replicaIndex =
+		index_open(RelationGetPrimaryKeyIndex(pgDistNode, false),
+				   AccessShareLock);
+#else
+	Relation replicaIndex =
+		index_open(RelationGetPrimaryKeyIndex(pgDistNode),
+				   AccessShareLock);
+#endif
+
 
 	ScanKeyInit(&scanKey[0], Anum_pg_dist_node_nodename,
 				BTEqualStrategyNumber, F_TEXTEQ, CStringGetTextDatum(nodeName));

src/backend/distributed/operations/node_protocol.c

@@ -746,7 +746,12 @@ GetRelationIdentityOrPK(Relation rel)
 
 	if (!OidIsValid(idxoid))
 	{
+/* Determine the index OID of the primary key (PG18 adds a second parameter) */
+#if PG_VERSION_NUM >= PG_VERSION_18
+		idxoid = RelationGetPrimaryKeyIndex(rel, false);
+#else
 		idxoid = RelationGetPrimaryKeyIndex(rel);
+#endif
 	}
 
 	return idxoid;

src/backend/distributed/operations/worker_copy_table_to_node_udf.c

@@ -13,6 +13,7 @@
 
 #include "postgres.h"
 
+#include "executor/executor.h"    /* for CreateExecutorState(), FreeExecutorState(), CreateExprContext(), etc. */
 #include "utils/builtins.h"
 #include "utils/lsyscache.h"
 

src/backend/distributed/planner/multi_explain.c

@@ -44,6 +44,11 @@
 #include "utils/snapmgr.h"
 
 #include "pg_version_constants.h"
+#if PG_VERSION_NUM >= PG_VERSION_18
+#include "commands/explain_dr.h"   /* CreateExplainSerializeDestReceiver() */
+#include "commands/explain_format.h"
+#endif
+
 
 #include "distributed/citus_depended_object.h"
 #include "distributed/citus_nodefuncs.h"
@@ -134,7 +139,7 @@ typedef struct ExplainAnalyzeDestination
 	TupleDesc lastSavedExplainAnalyzeTupDesc;
 } ExplainAnalyzeDestination;
 
-#if PG_VERSION_NUM >= PG_VERSION_17
+#if PG_VERSION_NUM >= PG_VERSION_17 && PG_VERSION_NUM < PG_VERSION_18
 
 /*
  * Various places within need to convert bytes to kilobytes.  Round these up
@@ -529,19 +534,53 @@ ExplainSubPlans(DistributedPlan *distributedPlan, ExplainState *es)
 
 		ExplainOpenGroup("PlannedStmt", "PlannedStmt", false, es);
 
+/* Capture memory stats on PG17+ */
 #if PG_VERSION_NUM >= PG_VERSION_17
 		if (es->memory)
 		{
 			MemoryContextSwitchTo(saved_ctx);
 			MemoryContextMemConsumed(planner_ctx, &mem_counters);
 		}
+#endif
 
-		ExplainOnePlan(plan, into, es, queryString, params, NULL, &planduration,
-					   (es->buffers ? &bufusage : NULL),
-					   (es->memory ? &mem_counters : NULL));
+#if PG_VERSION_NUM >= PG_VERSION_18
+		ExplainOnePlan(
+			plan,                            /* PlannedStmt *plannedstmt */
+			NULL,                            /* CachedPlan *cplan */
+			NULL,                            /* CachedPlanSource *plansource */
+			0,                               /* query_index */
+			into,                            /* IntoClause *into */
+			es,                              /* struct ExplainState *es */
+			queryString,                     /* const char *queryString */
+			params,                          /* ParamListInfo params */
+			NULL,                            /* QueryEnvironment *queryEnv */
+			&planduration,                   /* const instr_time *planduration */
+			(es->buffers ? &bufusage : NULL),/* const BufferUsage *bufusage */
+			(es->memory ? &mem_counters : NULL)  /* const MemoryContextCounters *mem_counters */
+			);
+#elif PG_VERSION_NUM >= PG_VERSION_17
+		ExplainOnePlan(
+			plan,
+			into,
+			es,
+			queryString,
+			params,
+			NULL,                           /* QueryEnvironment *queryEnv */
+			&planduration,
+			(es->buffers ? &bufusage : NULL),
+			(es->memory ? &mem_counters : NULL)
+			);
 #else
-		ExplainOnePlan(plan, into, es, queryString, params, NULL, &planduration,
-					   (es->buffers ? &bufusage : NULL));
+		ExplainOnePlan(
+			plan,
+			into,
+			es,
+			queryString,
+			params,
+			NULL,                           /* QueryEnvironment *queryEnv */
+			&planduration,
+			(es->buffers ? &bufusage : NULL)
+			);
 #endif
 
 		ExplainCloseGroup("PlannedStmt", "PlannedStmt", false, es);
@@ -1558,22 +1597,55 @@ CitusExplainOneQuery(Query *query, int cursorOptions, IntoClause *into,
 		BufferUsageAccumDiff(&bufusage, &pgBufferUsage, &bufusage_start);
 	}
 
+/* capture memory stats on PG17+ */
 #if PG_VERSION_NUM >= PG_VERSION_17
 	if (es->memory)
 	{
 		MemoryContextSwitchTo(saved_ctx);
 		MemoryContextMemConsumed(planner_ctx, &mem_counters);
 	}
+#endif
 
-	/* run it (if needed) and produce output */
-	ExplainOnePlan(plan, into, es, queryString, params, queryEnv,
-				   &planduration, (es->buffers ? &bufusage : NULL),
-				   (es->memory ? &mem_counters : NULL));
+#if PG_VERSION_NUM >= PG_VERSION_18
+	ExplainOnePlan(
+		plan,                          /* PlannedStmt *plannedstmt */
+		NULL,                          /* no CachedPlan */
+		NULL,                          /* no CachedPlanSource */
+		0,                             /* query_index */
+		into,                          /* IntoClause *into */
+		es,                            /* struct ExplainState *es */
+		queryString,                   /* const char *queryString */
+		params,                        /* ParamListInfo params */
+		queryEnv,                      /* QueryEnvironment *queryEnv */
+		&planduration,                 /* const instr_time *planduration */
+		(es->buffers ? &bufusage : NULL),   /* const BufferUsage *bufusage */
+		(es->memory ? &mem_counters : NULL) /* const MemoryContextCounters *mem_counters */
+		);
+#elif PG_VERSION_NUM >= PG_VERSION_17
+
+	/* PostgreSQL 17 signature (9 args: includes mem_counters) */
+	ExplainOnePlan(
+		plan,
+		into,
+		es,
+		queryString,
+		params,
+		queryEnv,
+		&planduration,
+		(es->buffers ? &bufusage : NULL),
+		(es->memory ? &mem_counters : NULL)
+		);
 #else
-
-	/* run it (if needed) and produce output */
-	ExplainOnePlan(plan, into, es, queryString, params, queryEnv,
-				   &planduration, (es->buffers ? &bufusage : NULL));
+	ExplainOnePlan(
+		plan,
+		into,
+		es,
+		queryString,
+		params,
+		queryEnv,
+		&planduration,
+		(es->buffers ? &bufusage : NULL)
+		);
 #endif
 }
 
@@ -1805,7 +1877,7 @@ WrapQueryForExplainAnalyze(const char *queryString, TupleDesc tupleDesc,
 			appendStringInfoString(columnDef, ", ");
 		}
 
-		Form_pg_attribute attr = &tupleDesc->attrs[columnIndex];
+		Form_pg_attribute attr = TupleDescAttr(tupleDesc, columnIndex);
 		char *attrType = format_type_extended(attr->atttypid, attr->atttypmod,
 											  FORMAT_TYPE_TYPEMOD_GIVEN |
 											  FORMAT_TYPE_FORCE_QUALIFY);
@@ -2026,21 +2098,55 @@ ExplainOneQuery(Query *query, int cursorOptions,
 			BufferUsageAccumDiff(&bufusage, &pgBufferUsage, &bufusage_start);
 		}
 
+/* 1) Capture memory counters on PG17+ only once: */
 #if PG_VERSION_NUM >= PG_VERSION_17
 		if (es->memory)
 		{
 			MemoryContextSwitchTo(saved_ctx);
 			MemoryContextMemConsumed(planner_ctx, &mem_counters);
 		}
-		/* run it (if needed) and produce output */
-		ExplainOnePlan(plan, into, es, queryString, params, queryEnv,
-					   &planduration, (es->buffers ? &bufusage : NULL),
-					   (es->memory ? &mem_counters : NULL));
-#else
-		/* run it (if needed) and produce output */
-		ExplainOnePlan(plan, into, es, queryString, params, queryEnv,
-					   &planduration, (es->buffers ? &bufusage : NULL));
 #endif
+
+#if PG_VERSION_NUM >= PG_VERSION_18
+		ExplainOnePlan(
+			plan,                 /* PlannedStmt *plannedstmt */
+			NULL,                 /* CachedPlan *cplan */
+			NULL,                 /* CachedPlanSource *plansource */
+			0,                    /* query_index */
+			into,                 /* IntoClause *into */
+			es,                   /* struct ExplainState *es */
+			queryString,          /* const char *queryString */
+			params,               /* ParamListInfo params */
+			queryEnv,             /* QueryEnvironment *queryEnv */
+			&planduration,        /* const instr_time *planduration */
+			(es->buffers  ? &bufusage    : NULL),
+			(es->memory   ? &mem_counters: NULL)
+		);
+#elif PG_VERSION_NUM >= PG_VERSION_17
+		ExplainOnePlan(
+			plan,
+			into,
+			es,
+			queryString,
+			params,
+			queryEnv,
+			&planduration,
+			(es->buffers  ? &bufusage    : NULL),
+			(es->memory   ? &mem_counters: NULL)
+		);
+#else
+		ExplainOnePlan(
+			plan,
+			into,
+			es,
+			queryString,
+			params,
+			queryEnv,
+			&planduration,
+			(es->buffers ? &bufusage : NULL)
+		);
+#endif
+
 	}
 }
 
@@ -2102,9 +2208,30 @@ ExplainWorkerPlan(PlannedStmt *plannedstmt, DestReceiver *dest, ExplainState *es
 	UpdateActiveSnapshotCommandId();
 
 	/* Create a QueryDesc for the query */
-	queryDesc = CreateQueryDesc(plannedstmt, queryString,
-								GetActiveSnapshot(), InvalidSnapshot,
-								dest, params, queryEnv, instrument_option);
+	#if PG_VERSION_NUM >= PG_VERSION_18
+	queryDesc = CreateQueryDesc(
+		plannedstmt,    /* PlannedStmt *plannedstmt */
+		NULL,           /* CachedPlan *cplan (none) */
+		queryString,    /* const char *sourceText */
+		GetActiveSnapshot(),   /* Snapshot snapshot */
+		InvalidSnapshot,       /* Snapshot crosscheck_snapshot */
+		dest,           /* DestReceiver *dest */
+		params,         /* ParamListInfo params */
+		queryEnv,       /* QueryEnvironment *queryEnv */
+		instrument_option /* int instrument_options */
+	);
+	#else
+	queryDesc = CreateQueryDesc(
+		plannedstmt,    /* PlannedStmt *plannedstmt */
+		queryString,    /* const char *sourceText */
+		GetActiveSnapshot(),   /* Snapshot snapshot */
+		InvalidSnapshot,       /* Snapshot crosscheck_snapshot */
+		dest,           /* DestReceiver *dest */
+		params,         /* ParamListInfo params */
+		queryEnv,       /* QueryEnvironment *queryEnv */
+		instrument_option /* int instrument_options */
+	);
+	#endif
 
 	/* Select execution options */
 	if (es->analyze)
@@ -2121,7 +2248,14 @@ ExplainWorkerPlan(PlannedStmt *plannedstmt, DestReceiver *dest, ExplainState *es
 		ScanDirection dir = ForwardScanDirection;
 
 		/* run the plan */
-		ExecutorRun(queryDesc, dir, 0L, true);
+/* run the plan: count = 0 (all rows) */
+#if PG_VERSION_NUM >= PG_VERSION_18
+    /* PG 18+ dropped the “execute_once” boolean */
+    ExecutorRun(queryDesc, dir, 0L);
+#else
+    /* PG 17- still expect the 4th ‘once’ argument */
+    ExecutorRun(queryDesc, dir, 0L, true);
+#endif
 
 		/* run cleanup too */
 		ExecutorFinish(queryDesc);
@@ -2135,7 +2269,7 @@ ExplainWorkerPlan(PlannedStmt *plannedstmt, DestReceiver *dest, ExplainState *es
 	/* Create textual dump of plan tree */
 	ExplainPrintPlan(es, queryDesc);
 
-#if PG_VERSION_NUM >= PG_VERSION_17
+#if PG_VERSION_NUM >= PG_VERSION_17 && PG_VERSION_NUM < PG_VERSION_18
 	/* Show buffer and/or memory usage in planning */
 	if (peek_buffer_usage(es, bufusage) || mem_counters)
 	{
@@ -2181,7 +2315,7 @@ ExplainWorkerPlan(PlannedStmt *plannedstmt, DestReceiver *dest, ExplainState *es
 	if (es->costs)
 		ExplainPrintJITSummary(es, queryDesc);
 
-#if PG_VERSION_NUM >= PG_VERSION_17
+#if PG_VERSION_NUM >= PG_VERSION_17 && PG_VERSION_NUM < PG_VERSION_18
 	if (es->serialize != EXPLAIN_SERIALIZE_NONE)
 	{
 		/* the SERIALIZE option requires its own tuple receiver */
@@ -2248,7 +2382,7 @@ elapsed_time(instr_time *starttime)
 }
 
 
-#if PG_VERSION_NUM >= PG_VERSION_17
+#if PG_VERSION_NUM >= PG_VERSION_17 && PG_VERSION_NUM < PG_VERSION_18
 /*
  * Return whether show_buffer_usage would have anything to print, if given
  * the same 'usage' data.  Note that when the format is anything other than
@@ -2560,7 +2694,7 @@ ExplainPrintSerialize(ExplainState *es, SerializeMetrics *metrics)
 			ExplainPropertyFloat("Time", "ms",
 								 1000.0 * INSTR_TIME_GET_DOUBLE(metrics->timeSpent),
 								 3, es);
-		ExplainPropertyUInteger("Output Volume", "kB",
+		ExplainPropertyInteger("Output Volume", "kB",
 								BYTES_TO_KILOBYTES(metrics->bytesSent), es);
 		ExplainPropertyText("Format", format, es);
 		if (es->buffers)

src/backend/distributed/planner/multi_logical_planner.c

@@ -35,6 +35,10 @@
 #include "utils/syscache.h"
 
 #include "pg_version_constants.h"
+#if PG_VERSION_NUM >= PG_VERSION_18
+typedef OpIndexInterpretation OpBtreeInterpretation;
+#endif
+
 
 #include "distributed/citus_clauses.h"
 #include "distributed/colocation_utils.h"
@@ -61,6 +65,11 @@ typedef struct QualifierWalkerContext
 } QualifierWalkerContext;
 
 
+#if PG_VERSION_NUM >= PG_VERSION_18
+#define get_op_btree_interpretation(opno) get_op_index_interpretation(opno)
+#endif
+
+
 /* Function pointer type definition for apply join rule functions */
 typedef MultiNode *(*RuleApplyFunction) (MultiNode *leftNode, MultiNode *rightNode,
 										 List *partitionColumnList, JoinType joinType,
@@ -2293,7 +2302,12 @@ OperatorImplementsEquality(Oid opno)
 	{
 		OpBtreeInterpretation *btreeIntepretation = (OpBtreeInterpretation *)
 													lfirst(btreeInterpretationCell);
+
+	#if PG_VERSION_NUM >= PG_VERSION_18
+		if (btreeIntepretation->cmptype == BTEqualStrategyNumber)
+	#else
 		if (btreeIntepretation->strategy == BTEqualStrategyNumber)
+	#endif
 		{
 			equalityOperator = true;
 			break;

src/backend/distributed/planner/multi_physical_planner.c

@@ -1418,8 +1418,24 @@ ExtractColumns(RangeTblEntry *callingRTE, int rangeTableId,
 	int subLevelsUp = 0;
 	int location = -1;
 	bool includeDroppedColumns = false;
-	expandRTE(callingRTE, rangeTableId, subLevelsUp, location, includeDroppedColumns,
-			  columnNames, columnVars);
+#if PG_VERSION_NUM >= PG_VERSION_18
+	expandRTE(callingRTE,
+			  rangeTableId,
+			  subLevelsUp,
+			  VAR_RETURNING_DEFAULT,    /* new argument on PG 18+ */
+			  location,
+			  includeDroppedColumns,
+			  columnNames,
+			  columnVars);
+#else
+	expandRTE(callingRTE,
+			  rangeTableId,
+			  subLevelsUp,
+			  location,
+			  includeDroppedColumns,
+			  columnNames,
+			  columnVars);
+#endif
 }
 
 

src/backend/distributed/planner/shard_pruning.c

@@ -85,6 +85,10 @@
 #include "utils/ruleutils.h"
 
 #include "pg_version_constants.h"
+#if PG_VERSION_NUM >= PG_VERSION_18
+typedef OpIndexInterpretation OpBtreeInterpretation;
+#endif
+
 
 #include "distributed/distributed_planner.h"
 #include "distributed/listutils.h"
@@ -177,6 +181,11 @@ typedef struct PruningInstance
 	bool isPartial;
 } PruningInstance;
 
+#if PG_VERSION_NUM >= PG_VERSION_18
+#define get_op_btree_interpretation(opno) get_op_index_interpretation(opno)
+#define ROWCOMPARE_NE COMPARE_NE
+#endif
+
 
 /*
  * Partial instances that need to be finished building. This is used to
@@ -1078,7 +1087,11 @@ IsValidPartitionKeyRestriction(OpExpr *opClause)
 		OpBtreeInterpretation *btreeInterpretation =
 			(OpBtreeInterpretation *) lfirst(btreeInterpretationCell);
 
+	#if PG_VERSION_NUM >= PG_VERSION_18
+		if (btreeInterpretation->cmptype == ROWCOMPARE_NE)
+	#else
 		if (btreeInterpretation->strategy == ROWCOMPARE_NE)
+	#endif
 		{
 			/* TODO: could add support for this, if we feel like it */
 			return false;
@@ -1130,7 +1143,11 @@ AddPartitionKeyRestrictionToInstance(ClauseWalkerContext *context, OpExpr *opCla
 		OpBtreeInterpretation *btreeInterpretation =
 			(OpBtreeInterpretation *) lfirst(btreeInterpretationCell);
 
+	#if PG_VERSION_NUM >= PG_VERSION_18
+		switch (btreeInterpretation->cmptype)
+	#else
 		switch (btreeInterpretation->strategy)
+	#endif
 		{
 			case BTLessStrategyNumber:
 			{
@@ -1299,7 +1316,11 @@ IsValidHashRestriction(OpExpr *opClause)
 		OpBtreeInterpretation *btreeInterpretation =
 			(OpBtreeInterpretation *) lfirst(btreeInterpretationCell);
 
+		#if PG_VERSION_NUM >= PG_VERSION_18
+		if (btreeInterpretation->cmptype == BTGreaterEqualStrategyNumber)
+		#else
 		if (btreeInterpretation->strategy == BTGreaterEqualStrategyNumber)
+		#endif
 		{
 			return true;
 		}

src/backend/distributed/shared_library_init.c

@@ -383,6 +383,33 @@ static const struct config_enum_entry metadata_sync_mode_options[] = {
 /* *INDENT-ON* */
 
 
+/*----------------------------------------------------------------------*
+* On PG 18+ the hook signatures changed; we wrap the old Citus handlers
+* in fresh functions that match the new typedefs exactly.
+*----------------------------------------------------------------------*/
+#if PG_VERSION_NUM >= PG_VERSION_18
+static bool
+citus_executor_start_adapter(QueryDesc *queryDesc, int eflags)
+{
+	/* call the original Citus hook (void) and always return “true” */
+	CitusExecutorStart(queryDesc, eflags);
+	return true;
+}
+
+
+static void
+citus_executor_run_adapter(QueryDesc *queryDesc,
+						   ScanDirection direction,
+						   uint64 count)
+{
+	/* call the original Citus hook (which still expects the old 4-arg form) */
+	CitusExecutorRun(queryDesc, direction, count, true);
+}
+
+
+#endif
+
+
 /* shared library initialization function */
 void
 _PG_init(void)
@@ -457,8 +484,13 @@ _PG_init(void)
 	set_rel_pathlist_hook = multi_relation_restriction_hook;
 	get_relation_info_hook = multi_get_relation_info_hook;
 	set_join_pathlist_hook = multi_join_restriction_hook;
+#if PG_VERSION_NUM >= PG_VERSION_18
+	ExecutorStart_hook = citus_executor_start_adapter;
+	ExecutorRun_hook = citus_executor_run_adapter;
+#else
 	ExecutorStart_hook = CitusExecutorStart;
 	ExecutorRun_hook = CitusExecutorRun;
+#endif
 	ExplainOneQuery_hook = CitusExplainOneQuery;
 	prev_ExecutorEnd = ExecutorEnd_hook;
 	ExecutorEnd_hook = CitusAttributeToEnd;

src/backend/distributed/test/fake_am.c

@@ -485,6 +485,7 @@ fake_estimate_rel_size(Relation rel, int32 *attr_widths,
  * Executor related callbacks for the fake AM
  * ------------------------------------------------------------------------
  */
+#if PG_VERSION_NUM < PG_VERSION_18
 static bool
 fake_scan_bitmap_next_block(TableScanDesc scan,
 							TBMIterateResult *tbmres)
@@ -502,6 +503,8 @@ fake_scan_bitmap_next_tuple(TableScanDesc scan,
 }
 
 
+#endif
+
 static bool
 fake_scan_sample_next_block(TableScanDesc scan,
 							SampleScanState *scanstate)
@@ -578,8 +581,13 @@ static const TableAmRoutine fake_methods = {
 
 	.relation_estimate_size = fake_estimate_rel_size,
 
+#if PG_VERSION_NUM < PG_VERSION_18
+
+	/* these two fields were removed in PG 18 */
 	.scan_bitmap_next_block = fake_scan_bitmap_next_block,
 	.scan_bitmap_next_tuple = fake_scan_bitmap_next_tuple,
+#endif
+
 	.scan_sample_next_block = fake_scan_sample_next_block,
 	.scan_sample_next_tuple = fake_scan_sample_next_tuple
 };

src/backend/distributed/transaction/relation_access_tracking.c

@@ -21,6 +21,7 @@
 #include "common/hashfn.h"
 #include "utils/hsearch.h"
 #include "utils/lsyscache.h"
+#include "utils/memutils.h"    /* for ALLOCSET_DEFAULT_MINSIZE, _INITSIZE, _MAXSIZE */
 
 #include "pg_version_constants.h"
 

src/backend/distributed/transaction/transaction_recovery.c

@@ -514,8 +514,9 @@ PendingWorkerTransactionList(MultiConnection *connection)
 	List *transactionNames = NIL;
 	int32 coordinatorId = GetLocalGroupId();
 
-	appendStringInfo(command, "SELECT gid FROM pg_prepared_xacts "
-							  "WHERE gid LIKE 'citus\\_%d\\_%%' and database = current_database()",
+	appendStringInfo(command,
+					 "SELECT gid FROM pg_prepared_xacts "
+					 "WHERE gid COLLATE pg_catalog.default LIKE 'citus\\_%d\\_%%' COLLATE pg_catalog.default AND database = current_database()",
 					 coordinatorId);
 
 	int querySent = SendRemoteCommand(connection, command->data);

src/backend/distributed/utils/aggregate_utils.c

@@ -918,7 +918,7 @@ TypecheckWorkerPartialAggArgType(FunctionCallInfo fcinfo, StypeBox *box)
 										true, 'i', &argtypesNull);
 			Assert(!argtypesNull);
 			TupleDesc tupleDesc = box->aggregationArgumentContext->tupleDesc;
-			if (argType != tupleDesc->attrs[aggregateArgIndex].atttypid)
+			if (argType != TupleDescAttr(tupleDesc, aggregateArgIndex)->atttypid)
 			{
 				return false;
 			}

src/backend/distributed/utils/background_jobs.c

@@ -1906,7 +1906,32 @@ ExecuteSqlString(const char *sql)
 
 		/* Don't display the portal in pg_cursors */
 		portal->visible = false;
-		PortalDefineQuery(portal, NULL, sql, commandTag, plantree_list, NULL);
+
+		#if PG_VERSION_NUM >= PG_VERSION_18
+
+		/* PG18+ added a seventh “plansource” argument */
+		PortalDefineQuery(
+			portal,
+			NULL,             /* no prepared‐stmt name */
+			sql,              /* the query text */
+			commandTag,       /* the CommandTag */
+			plantree_list,    /* List of PlannedStmt* */
+			NULL,             /* no CachedPlan */
+			NULL              /* no CachedPlanSource */
+			);
+	#else
+
+		/* PG17-: six‐arg signature */
+		PortalDefineQuery(
+			portal,
+			NULL,             /* no prepared‐stmt name */
+			sql,              /* the query text */
+			commandTag,       /* the CommandTag */
+			plantree_list,    /* List of PlannedStmt* */
+			NULL              /* no CachedPlan */
+			);
+	#endif
+
 		PortalStart(portal, NULL, 0, InvalidSnapshot);
 		int16 format[] = { 1 };
 		PortalSetResultFormat(portal, lengthof(format), format);        /* binary format */
@@ -1923,7 +1948,28 @@ ExecuteSqlString(const char *sql)
 
 		/* Here's where we actually execute the command. */
 		QueryCompletion qc = { 0 };
-		(void) PortalRun(portal, FETCH_ALL, isTopLevel, true, receiver, receiver, &qc);
+
+/* Execute the portal, dropping the `run_once` arg on PG18+ */
+#if PG_VERSION_NUM >= PG_VERSION_18
+		(void) PortalRun(
+			portal,
+			FETCH_ALL,  /* count */
+			isTopLevel, /* isTopLevel */
+			receiver,   /* DestReceiver *dest */
+			receiver,   /* DestReceiver *altdest */
+			&qc         /* QueryCompletion *qc */
+			);
+#else
+		(void) PortalRun(
+			portal,
+			FETCH_ALL,  /* count */
+			isTopLevel, /* isTopLevel */
+			true,       /* run_once */
+			receiver,   /* DestReceiver *dest */
+			receiver,   /* DestReceiver *altdest */
+			&qc         /* QueryCompletion *qc */
+			);
+#endif
 
 		/* Clean up the receiver. */
 		(*receiver->rDestroy)(receiver);

src/backend/distributed/utils/citus_depended_object.c

@@ -42,6 +42,7 @@
 #include "parser/parse_type.h"
 #include "storage/large_object.h"
 #include "utils/lsyscache.h"
+#include "utils/memutils.h"
 #include "utils/syscache.h"
 
 #include "distributed/citus_depended_object.h"

src/backend/distributed/utils/citus_nodefuncs.c

@@ -324,6 +324,16 @@ GetRangeTblKind(RangeTblEntry *rte)
 			break;
 		}
 
+		#if PG_VERSION_NUM >= PG_VERSION_18
+
+		/* new in PG18: GROUP RTE, just map it straight through */
+		case RTE_GROUP:
+		{
+			rteKind = (CitusRTEKind) rte->rtekind;
+			break;
+		}
+
+		#endif
 		case RTE_FUNCTION:
 		{
 			/*

src/backend/distributed/utils/colocation_utils.c

@@ -1362,9 +1362,21 @@ DeleteColocationGroupLocally(uint32 colocationId)
 		 * https://github.com/citusdata/citus/pull/2855#discussion_r313628554
 		 * https://github.com/citusdata/citus/issues/1890
 		 */
-		Relation replicaIndex =
-			index_open(RelationGetPrimaryKeyIndex(pgDistColocation),
-					   AccessShareLock);
+#if PG_VERSION_NUM >= PG_VERSION_18
+
+		/* PG 18+ expects a second “deferrable_ok” flag */
+		Relation replicaIndex = index_open(
+			RelationGetPrimaryKeyIndex(pgDistColocation, false),
+			AccessShareLock
+			);
+#else
+
+		/* PG 17- had a single-arg signature */
+		Relation replicaIndex = index_open(
+			RelationGetPrimaryKeyIndex(pgDistColocation),
+			AccessShareLock
+			);
+#endif
 		simple_heap_delete(pgDistColocation, &(heapTuple->t_self));
 
 		CitusInvalidateRelcacheByRelid(DistColocationRelationId());

src/backend/distributed/utils/enable_ssl.c

@@ -239,18 +239,28 @@ CreateCertificatesWhenNeeded()
 	SSL_CTX *sslContext = NULL;
 
 	/*
-	 * Since postgres might not have initialized ssl at this point we need to initialize
-	 * it our self to be able to create a context. This code is less extensive then
-	 * postgres' initialization but that will happen when postgres reloads its
-	 * configuration with ssl enabled.
+	 * Ensure the OpenSSL library is initialized so we can create our SSL context.
+	 * On OpenSSL ≥ 1.1.0 we call OPENSSL_init_ssl() (which also loads the default
+	 * config), and on older versions we fall back to SSL_library_init().
+	 * PostgreSQL itself will perform its full SSL setup when it reloads
+	 * its configuration with ssl enabled.
 	 */
-#ifdef HAVE_OPENSSL_INIT_SSL
+#if defined(OPENSSL_VERSION_NUMBER) && OPENSSL_VERSION_NUMBER >= 0x10100000L
+
+	/* OpenSSL 1.1.0+ */
 	OPENSSL_init_ssl(OPENSSL_INIT_LOAD_CONFIG, NULL);
 #else
+
+	/* OpenSSL < 1.1.0 */
 	SSL_library_init();
 #endif
 
+#if defined(OPENSSL_VERSION_NUMBER) && OPENSSL_VERSION_NUMBER >= 0x10100000L
+	sslContext = SSL_CTX_new(TLS_method());
+#else
 	sslContext = SSL_CTX_new(SSLv23_method());
+#endif
+
 	if (!sslContext)
 	{
 		ereport(WARNING, (errmsg("unable to create ssl context, please verify ssl "
@@ -379,8 +389,17 @@ CreateCertificate(EVP_PKEY *privateKey)
 	 * would fail right after an upgrade. Instead of working until the certificate
 	 * expiration date and then suddenly erroring out.
 	 */
+#if defined(OPENSSL_VERSION_NUMBER) && OPENSSL_VERSION_NUMBER >= 0x10100000L
+
+	/* New mutable accessors (present in 1.1, 3.x). */
+	X509_gmtime_adj(X509_getm_notBefore(certificate), 0);
+	X509_gmtime_adj(X509_getm_notAfter(certificate), 0);
+#else
+
+	/* Legacy functions kept for 1.0.x compatibility. */
 	X509_gmtime_adj(X509_get_notBefore(certificate), 0);
 	X509_gmtime_adj(X509_get_notAfter(certificate), 0);
+#endif
 
 	/* Set the public key for our certificate */
 	X509_set_pubkey(certificate, privateKey);

src/include/columnar/columnar_version_compat.h

@@ -9,14 +9,28 @@
  *-------------------------------------------------------------------------
  */
 
-#ifndef COLUMNAR_COMPAT_H
-#define COLUMNAR_COMPAT_H
+ #ifndef COLUMNAR_VERSION_COMPAT_H
+ #define COLUMNAR_VERSION_COMPAT_H
 
 #include "pg_version_constants.h"
 
+/* for PG_VERSION_NUM and TupleDescAttr() */
+#include "postgres.h"
+
+#include "access/htup_details.h"
+
+
 #define ACLCHECK_OBJECT_TABLE OBJECT_TABLE
 
 #define ExplainPropertyLong(qlabel, value, es) \
 	ExplainPropertyInteger(qlabel, NULL, value, es)
 
+
+/* tuple-descriptor attributes moved in PostgreSQL 18: */
+#if PG_VERSION_NUM >= PG_VERSION_18
+#define Attr(tupdesc, colno) TupleDescAttr((tupdesc), (colno))
+#else
+#define Attr(tupdesc, colno) (&((tupdesc)->attrs[(colno)]))
+#endif
+
 #endif /* COLUMNAR_COMPAT_H */

src/include/distributed/resource_lock.h

@@ -169,7 +169,7 @@ IsNodeWideObjectClass(ObjectClass objectClass)
 	 * If new object classes are added and none of them are node-wide, then update
 	 * this assertion check based on latest supported major Postgres version.
 	 */
-	StaticAssertStmt(PG_MAJORVERSION_NUM <= 17,
+	StaticAssertStmt(PG_MAJORVERSION_NUM <= 18,
 					 "better to check if any of newly added ObjectClass'es are node-wide");
 
 	switch (objectClass)

src/include/pg_version_compat.h

@@ -384,9 +384,35 @@ getStxstattarget_compat(HeapTuple tup)
 
 #define matched_compat(a) (a->matchKind == MERGE_WHEN_MATCHED)
 
-#define create_foreignscan_path_compat(a, b, c, d, e, f, g, h, i, j, \
-									   k) create_foreignscan_path(a, b, c, d, e, f, g, h, \
-																  i, j, k)
+#include "nodes/bitmapset.h"      /* for Relids */
+#include "nodes/pg_list.h"        /* for List */
+#include "optimizer/pathnode.h"   /* for create_foreignscan_path() */
+
+#if PG_VERSION_NUM >= PG_VERSION_18
+#define create_foreignscan_path_compat(a, b, c, d, e, f, g, h, i, j, k) \
+	create_foreignscan_path( \
+		(a),            /* root            */ \
+		(b),            /* rel             */ \
+		(c),            /* target          */ \
+		(d),            /* rows            */ \
+		0,              /* disabled_nodes  */ \
+		(e),            /* startup_cost    */ \
+		(f),            /* total_cost      */ \
+		(g),            /* pathkeys        */ \
+		(h),            /* required_outer  */ \
+		(i),            /* fdw_outerpath   */ \
+		(j),            /* fdw_restrictinfo*/ \
+		(k)             /* fdw_private     */ \
+		)
+#else
+#define create_foreignscan_path_compat(a, b, c, d, e, f, g, h, i, j, k) \
+	create_foreignscan_path( \
+		(a), (b), (c), (d), \
+		(e), (f), \
+		(g), (h), (i), (j), (k) \
+		)
+#endif
+
 
 #define getProcNo_compat(a) (a->vxid.procNumber)
 #define getLxid_compat(a) (a->vxid.lxid)

src/include/pg_version_constants.h

@@ -15,5 +15,6 @@
 #define PG_VERSION_16 160000
 #define PG_VERSION_17 170000
 #define PG_VERSION_18 180000
+#define PG_VERSION_19 190000
 
 #endif   /* PG_VERSION_CONSTANTS */