PG16 - Throw meaningful error for stats without a name on Citus tables (#7136)

Relevant PG commit:
624aa2a13b
624aa2a13bd02dd584bb0995c883b5b93b2152df

src/backend/distributed/commands/statistics.c

@@ -77,6 +77,14 @@ PreprocessCreateStatisticsStmt(Node *node, const char *queryString,
 
 	EnsureCoordinator();
 
+	if (!(stmt->defnames))
+	{
+		ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+						errmsg("cannot create statistics without a name on a "
+							   "Citus table"),
+						errhint("Consider specifying a name for the statistics")));
+	}
+
 	QualifyTreeNode((Node *) stmt);
 
 	Oid statsOid = get_statistics_object_oid(stmt->defnames, true);

src/test/regress/expected/pg16.out

@@ -65,6 +65,28 @@ SET citus.log_remote_commands TO OFF;
 -- only verifying it works and not printing log
 -- remote commands because it can be flaky
 VACUUM (ONLY_DATABASE_STATS);
+-- Proper error when creating statistics without a name on a Citus table
+-- Relevant PG commit:
+-- https://github.com/postgres/postgres/commit/624aa2a13bd02dd584bb0995c883b5b93b2152df
+CREATE TABLE test_stats (
+    a   int,
+    b   int
+);
+SELECT create_distributed_table('test_stats', 'a');
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+CREATE STATISTICS (dependencies) ON a, b FROM test_stats;
+ERROR:  cannot create statistics without a name on a Citus table
+HINT:  Consider specifying a name for the statistics
+CREATE STATISTICS (ndistinct, dependencies) on a, b from test_stats;
+ERROR:  cannot create statistics without a name on a Citus table
+HINT:  Consider specifying a name for the statistics
+CREATE STATISTICS (ndistinct, dependencies, mcv) on a, b from test_stats;
+ERROR:  cannot create statistics without a name on a Citus table
+HINT:  Consider specifying a name for the statistics
 \set VERBOSITY terse
 SET client_min_messages TO ERROR;
 DROP SCHEMA pg16 CASCADE;

src/test/regress/sql/pg16.sql

@@ -45,6 +45,21 @@ SET citus.log_remote_commands TO OFF;
 -- remote commands because it can be flaky
 VACUUM (ONLY_DATABASE_STATS);
 
+-- Proper error when creating statistics without a name on a Citus table
+-- Relevant PG commit:
+-- https://github.com/postgres/postgres/commit/624aa2a13bd02dd584bb0995c883b5b93b2152df
+
+CREATE TABLE test_stats (
+    a   int,
+    b   int
+);
+
+SELECT create_distributed_table('test_stats', 'a');
+
+CREATE STATISTICS (dependencies) ON a, b FROM test_stats;
+CREATE STATISTICS (ndistinct, dependencies) on a, b from test_stats;
+CREATE STATISTICS (ndistinct, dependencies, mcv) on a, b from test_stats;
+
 \set VERBOSITY terse
 SET client_min_messages TO ERROR;
 DROP SCHEMA pg16 CASCADE;