add isolation tests that show reference table creation doesn't block anymore

src/test/regress/expected/isolation_reference_table.out

@@ -0,0 +1,105 @@
+unused step name: s1-abort
+unused step name: s2-abort
+Parsed test spec with 2 sessions
+
+starting permutation: s1-begin s1-create s2-create s1-commit
+create_reference_table
+---------------------------------------------------------------------
+
+(1 row)
+
+step s1-begin:
+    BEGIN;
+
+step s1-create:
+    CREATE TABLE reference_table_s1(a int);
+ 	SELECT create_reference_table('reference_table_s1');
+
+create_reference_table
+---------------------------------------------------------------------
+
+(1 row)
+
+step s2-create:
+    CREATE TABLE reference_table_s2(a int);
+ 	SELECT create_reference_table('reference_table_s2');
+
+create_reference_table
+---------------------------------------------------------------------
+
+(1 row)
+
+step s1-commit:
+    COMMIT;
+
+
+starting permutation: s1-create s2-create s1-begin s1-drop s2-drop s1-commit
+create_reference_table
+---------------------------------------------------------------------
+
+(1 row)
+
+step s1-create:
+    CREATE TABLE reference_table_s1(a int);
+ 	SELECT create_reference_table('reference_table_s1');
+
+create_reference_table
+---------------------------------------------------------------------
+
+(1 row)
+
+step s2-create:
+    CREATE TABLE reference_table_s2(a int);
+ 	SELECT create_reference_table('reference_table_s2');
+
+create_reference_table
+---------------------------------------------------------------------
+
+(1 row)
+
+step s1-begin:
+    BEGIN;
+
+step s1-drop:
+    DROP TABLE reference_table_s1;
+
+step s2-drop:
+    DROP TABLE reference_table_s2;
+
+step s1-commit:
+    COMMIT;
+
+
+starting permutation: s1-create s2-begin s2-create s1-drop s2-commit
+create_reference_table
+---------------------------------------------------------------------
+
+(1 row)
+
+step s1-create:
+    CREATE TABLE reference_table_s1(a int);
+ 	SELECT create_reference_table('reference_table_s1');
+
+create_reference_table
+---------------------------------------------------------------------
+
+(1 row)
+
+step s2-begin:
+    BEGIN;
+
+step s2-create:
+    CREATE TABLE reference_table_s2(a int);
+ 	SELECT create_reference_table('reference_table_s2');
+
+create_reference_table
+---------------------------------------------------------------------
+
+(1 row)
+
+step s1-drop:
+    DROP TABLE reference_table_s1;
+
+step s2-commit:
+    COMMIT;
+

src/test/regress/isolation_schedule

@@ -69,6 +69,7 @@ test: isolation_undistribute_table
 test: isolation_fix_partition_shard_index_names
 test: isolation_global_pid
 test: isolation_citus_locks
+test: isolation_reference_table
 
 # Rebalancer
 test: isolation_blocking_move_single_shard_commands

src/test/regress/spec/isolation_reference_table.spec

@@ -0,0 +1,80 @@
+// reference tables _do_ lock on the first reference table in the shardgroup due to the lack of shardgroups in the
+// system. When we run the tests we want to make sure the tables we are testing against cannot be the first reference
+// table. For this purpose we create a reference table that we will _not_ interact with during the tests.
+setup
+{
+ 	CREATE TABLE first_reference_table(a int);
+ 	SELECT create_reference_table('first_reference_table');
+}
+
+teardown
+{
+    DROP TABLE first_reference_table;
+    DROP TABLE IF EXISTS reference_table_s1;
+    DROP TABLE IF EXISTS reference_table_s2;
+}
+
+session "s1"
+
+step "s1-begin"
+{
+    BEGIN;
+}
+
+step "s1-create"
+{
+    CREATE TABLE reference_table_s1(a int);
+ 	SELECT create_reference_table('reference_table_s1');
+}
+
+step "s1-drop"
+{
+    DROP TABLE reference_table_s1;
+}
+
+step "s1-abort"
+{
+    ABORT;
+}
+
+step "s1-commit"
+{
+    COMMIT;
+}
+
+session "s2"
+
+step "s2-begin"
+{
+    BEGIN;
+}
+
+step "s2-create"
+{
+    CREATE TABLE reference_table_s2(a int);
+ 	SELECT create_reference_table('reference_table_s2');
+}
+
+step "s2-drop"
+{
+    DROP TABLE reference_table_s2;
+}
+
+step "s2-abort"
+{
+    ABORT;
+}
+
+step "s2-commit"
+{
+    COMMIT;
+}
+
+// creates don't block each other
+permutation "s1-begin" "s1-create" "s2-create" "s1-commit"
+
+// drops don't block each other
+permutation "s1-create" "s2-create" "s1-begin" "s1-drop" "s2-drop" "s1-commit"
+
+// create and drop don't block each other
+permutation "s1-create" "s2-begin" "s2-create" "s1-drop" "s2-commit"