Fix segfault when executing DDL via UDF

src/backend/distributed/executor/multi_executor.c

@@ -479,6 +479,12 @@ ExecuteQueryIntoDestReceiver(Query *query, ParamListInfo params, DestReceiver *d
 {
 	int cursorOptions = CURSOR_OPT_PARALLEL_OK;
 
+	if (query->commandType == CMD_UTILITY)
+	{
+		/* can only execute DML/SELECT via this path */
+		ereport(ERROR, (errmsg("cannot execute utility commands")));
+	}
+
 	/* plan the subquery, this may be another distributed query */
 	PlannedStmt *queryPlan = pg_plan_query(query, cursorOptions, params);
 

src/test/regress/expected/intermediate_results.out

@@ -252,6 +252,13 @@ SELECT * FROM squares ORDER BY x;
 -- empty shard interval array should raise error
 SELECT worker_hash_partition_table(42,1,'SELECT a FROM generate_series(1,100) AS a', 'a', 23, ARRAY[0]);
 ERROR:  invalid distribution column value
+-- cannot use DDL commands
+select broadcast_intermediate_result('a', 'create table foo(int serial)');
+ERROR:  cannot execute utility commands
+select broadcast_intermediate_result('a', 'prepare foo as select 1');
+ERROR:  cannot execute utility commands
+select create_intermediate_result('a', 'create table foo(int serial)');
+ERROR:  cannot execute utility commands
 DROP SCHEMA intermediate_results CASCADE;
 NOTICE:  drop cascades to 5 other objects
 DETAIL:  drop cascades to table interesting_squares

src/test/regress/expected/worker_check_invalid_arguments.out

@@ -67,7 +67,7 @@ ERROR:  column name array size: 2 and type array size: 3 do not match
 SELECT worker_merge_files_into_table(:JobId, :TaskId,
        				     ARRAY['textcolumn', 'binarycolumn'],
 				     ARRAY['text', 'integer']);
-ERROR:  invalid input syntax for type integer: "\x0b50"
+ERROR:  invalid input syntax for integer: "\x0b50"
 CONTEXT:  COPY task_101108, line 1, column binarycolumn: "\x0b50"
 -- Check that we fail to merge when ids are wrong
 SELECT worker_merge_files_into_table(-1, :TaskId,
@@ -97,3 +97,6 @@ SELECT worker_merge_files_into_table(:JobId, :TaskId,
  
 (1 row)
 
+-- worker_execute_sql_task should only accept queries
+select worker_execute_sql_task(0,0,'create table foo(a serial)',false);
+ERROR:  cannot execute utility commands

src/test/regress/sql/intermediate_results.sql

@@ -143,4 +143,9 @@ SELECT * FROM squares ORDER BY x;
 -- empty shard interval array should raise error
 SELECT worker_hash_partition_table(42,1,'SELECT a FROM generate_series(1,100) AS a', 'a', 23, ARRAY[0]);
 
+-- cannot use DDL commands
+select broadcast_intermediate_result('a', 'create table foo(int serial)');
+select broadcast_intermediate_result('a', 'prepare foo as select 1');
+select create_intermediate_result('a', 'create table foo(int serial)');
+
 DROP SCHEMA intermediate_results CASCADE;

src/test/regress/sql/worker_check_invalid_arguments.sql

@@ -100,3 +100,6 @@ SELECT worker_merge_files_and_run_query(:JobId, -1,
 SELECT worker_merge_files_into_table(:JobId, :TaskId,
        				     ARRAY['textcolumn', 'binarycolumn'],
 				     ARRAY['text', 'bytea']);
+
+-- worker_execute_sql_task should only accept queries
+select worker_execute_sql_task(0,0,'create table foo(a serial)',false);