Allow distributed INSERT...SELECT via worker nodes in MX

src/backend/distributed/planner/insert_select_planner.c

@@ -321,14 +321,6 @@ DistributedInsertSelectSupported(Query *queryTree, RangeTblEntry *insertRte,
 							 NULL, NULL);
 	}
 
-	if (GetLocalGroupId() != 0)
-	{
-		return DeferredError(ERRCODE_FEATURE_NOT_SUPPORTED,
-							 "distributed INSERT ... SELECT can only be performed from "
-							 "the coordinator",
-							 NULL, NULL);
-	}
-
 	/* we do not expect to see a view in modify target */
 	foreach(rangeTableCell, queryTree->rtable)
 	{

src/test/regress/expected/multi_mx_modifications.out

@@ -428,14 +428,12 @@ SELECT * FROM multiple_hash_mx WHERE category = '2' ORDER BY category, data;
 INSERT INTO multiple_hash_mx
 SELECT s, s*2 FROM generate_series(1,10) s;
 INSERT 0 10
--- but are never distributed
+-- including distributed INSERT ... SELECT
 BEGIN;
 BEGIN
 SET LOCAL client_min_messages TO DEBUG1;
 SET
 INSERT INTO multiple_hash_mx SELECT * FROM multiple_hash_mx;
-DEBUG:  distributed INSERT ... SELECT can only be performed from the coordinator
-DEBUG:  Collecting INSERT ... SELECT results on coordinator
 INSERT 0 10
 END;
 COMMIT

src/test/regress/expected/multi_unsupported_worker_operations.out

@@ -264,19 +264,6 @@ SELECT count(*) FROM mx_table;
      5
 (1 row)
 
--- INSERT / SELECT pulls results to worker
-BEGIN;
-SET LOCAL client_min_messages TO DEBUG;
-INSERT INTO mx_table_2 SELECT * FROM mx_table;
-DEBUG:  distributed INSERT ... SELECT can only be performed from the coordinator
-DEBUG:  Collecting INSERT ... SELECT results on coordinator
-END;
-SELECT count(*) FROM mx_table_2;
- count 
--------
-     5
-(1 row)
-
 -- mark_tables_colocated
 UPDATE pg_dist_partition SET colocationid = 0 WHERE logicalrelid='mx_table_2'::regclass;
 SELECT mark_tables_colocated('mx_table', ARRAY['mx_table_2']);

src/test/regress/sql/multi_mx_modifications.sql

@@ -276,7 +276,7 @@ SELECT * FROM multiple_hash_mx WHERE category = '2' ORDER BY category, data;
 INSERT INTO multiple_hash_mx
 SELECT s, s*2 FROM generate_series(1,10) s;
 
--- but are never distributed
+-- including distributed INSERT ... SELECT
 BEGIN;
 SET LOCAL client_min_messages TO DEBUG1;
 INSERT INTO multiple_hash_mx SELECT * FROM multiple_hash_mx;

src/test/regress/sql/multi_unsupported_worker_operations.sql

@@ -138,14 +138,6 @@ SELECT master_remove_node('localhost', 5432);
 TRUNCATE mx_table;
 SELECT count(*) FROM mx_table;
 
--- INSERT / SELECT pulls results to worker
-BEGIN;
-SET LOCAL client_min_messages TO DEBUG;
-INSERT INTO mx_table_2 SELECT * FROM mx_table;
-END;
-
-SELECT count(*) FROM mx_table_2;
-
 -- mark_tables_colocated
 UPDATE pg_dist_partition SET colocationid = 0 WHERE logicalrelid='mx_table_2'::regclass;