Support intermediate results in distributed INSERT..SELECT

src/backend/distributed/planner/insert_select_planner.c

@@ -332,7 +332,7 @@ DistributedInsertSelectSupported(Query *queryTree, RangeTblEntry *insertRte,
 		}
 	}
 
-	if (contain_volatile_functions((Node *) queryTree))
+	if (FindNodeCheck((Node *) queryTree, CitusIsVolatileFunction))
 	{
 		return DeferredError(ERRCODE_FEATURE_NOT_SUPPORTED,
 							 "volatile functions are not allowed in distributed "

src/test/regress/expected/multi_insert_select.out

@@ -1775,6 +1775,25 @@ SELECT count(*) FROM raw_events_second;
     38
 (1 row)
 
+-- intermediate results (CTEs) should be allowed when doing INSERT...SELECT within a CTE
+WITH series AS (
+  SELECT s AS val FROM generate_series(60,70) s
+),
+inserts AS (
+  INSERT INTO raw_events_second (user_id)
+  SELECT
+    user_id
+  FROM
+    raw_events_first JOIN series ON (value_1 = val)
+  RETURNING
+    NULL
+)
+SELECT count(*) FROM inserts;
+ count 
+-------
+     2
+(1 row)
+
 -- we need this in our next test
 truncate raw_events_first;
 SET client_min_messages TO DEBUG2;

src/test/regress/sql/multi_insert_select.sql

@@ -1420,6 +1420,21 @@ INSERT INTO raw_events_first (user_id, time, value_1, value_2, value_3, value_4)
 INSERT INTO raw_events_second SELECT * FROM test_view WHERE user_id = 17 GROUP BY 1,2,3,4,5,6;
 SELECT count(*) FROM raw_events_second;
 
+-- intermediate results (CTEs) should be allowed when doing INSERT...SELECT within a CTE
+WITH series AS (
+  SELECT s AS val FROM generate_series(60,70) s
+),
+inserts AS (
+  INSERT INTO raw_events_second (user_id)
+  SELECT
+    user_id
+  FROM
+    raw_events_first JOIN series ON (value_1 = val)
+  RETURNING
+    NULL
+)
+SELECT count(*) FROM inserts;
+
 -- we need this in our next test
 truncate raw_events_first;