Merge pull request #1894 from citusdata/unions

Support set operations

src/backend/distributed/planner/multi_logical_planner.c

@@ -97,9 +97,6 @@ static bool RangeTableArrayContainsAnyRTEIdentities(RangeTblEntry **rangeTableEn
 													queryRteIdentities);
 static Relids QueryRteIdentities(Query *queryTree);
 static DeferredErrorMessage * DeferErrorIfFromClauseRecurs(Query *queryTree);
-static DeferredErrorMessage * DeferErrorIfUnsupportedUnionQuery(Query *queryTree,
-																bool
-																outerMostQueryHasLimit);
 static bool ExtractSetOperationStatmentWalker(Node *node, List **setOperationList);
 static DeferredErrorMessage * DeferErrorIfUnsupportedTableCombination(Query *queryTree);
 static bool WindowPartitionOnDistributionColumn(Query *query);
@@ -985,8 +982,7 @@ DeferErrorIfCannotPushdownSubquery(Query *subqueryTree, bool outerMostQueryHasLi
 
 	if (subqueryTree->setOperations)
 	{
-		deferredError = DeferErrorIfUnsupportedUnionQuery(subqueryTree,
+		deferredError = DeferErrorIfUnsupportedUnionQuery(subqueryTree);
-														  outerMostQueryHasLimit);
 		if (deferredError)
 		{
 			return deferredError;
@@ -1098,9 +1094,8 @@ DeferErrorIfCannotPushdownSubquery(Query *subqueryTree, bool outerMostQueryHasLi
  * DeferErrorIfUnsupportedUnionQuery is a helper function for ErrorIfCannotPushdownSubquery().
  * The function also errors out for set operations INTERSECT and EXCEPT.
  */
-static DeferredErrorMessage *
+DeferredErrorMessage *
-DeferErrorIfUnsupportedUnionQuery(Query *subqueryTree,
+DeferErrorIfUnsupportedUnionQuery(Query *subqueryTree)
-								  bool outerMostQueryHasLimit)
 {
 	List *setOperationStatementList = NIL;
 	ListCell *setOperationStatmentCell = NULL;
@@ -1534,6 +1529,17 @@ FindNodeCheckInRangeTableList(List *rtable, bool (*check)(Node *))
 }
 
 
+/*
+ * QueryContainsDistributedTableRTE determines whether the given
+ * query contains a distributed table.
+ */
+bool
+QueryContainsDistributedTableRTE(Query *query)
+{
+	return FindNodeCheck((Node *) query, IsDistributedTableRTE);
+}
+
+
 /*
  * IsDistributedTableRTE gets a node and returns true if the node
  * is a range table relation entry that points to a distributed

src/backend/distributed/planner/recursive_planning.c

@@ -67,10 +67,12 @@
 #include "distributed/relation_restriction_equivalence.h"
 #include "lib/stringinfo.h"
 #include "optimizer/planner.h"
+#include "parser/parsetree.h"
 #include "nodes/nodeFuncs.h"
 #include "nodes/nodes.h"
 #include "nodes/pg_list.h"
 #include "nodes/primnodes.h"
+#include "nodes/relation.h"
 #include "utils/builtins.h"
 #include "utils/guc.h"
 
@@ -117,6 +119,10 @@ static DeferredErrorMessage * RecursivelyPlanCTEs(Query *query,
 												  RecursivePlanningContext *context);
 static bool RecursivelyPlanSubqueryWalker(Node *node, RecursivePlanningContext *context);
 static bool ShouldRecursivelyPlanSubquery(Query *subquery);
+static bool ShouldRecursivelyPlanSetOperation(Query *query,
+											  RecursivePlanningContext *context);
+static void RecursivelyPlanSetOperations(Query *query, Node *node,
+										 RecursivePlanningContext *context);
 static bool IsLocalTableRTE(Node *node);
 static void RecursivelyPlanSubquery(Query *subquery,
 									RecursivePlanningContext *planningContext);
@@ -217,6 +223,21 @@ RecursivelyPlanSubqueriesAndCTEs(Query *query, RecursivePlanningContext *context
 	/* descend into subqueries */
 	query_tree_walker(query, RecursivelyPlanSubqueryWalker, context, 0);
 
+	/*
+	 * At this point, all CTEs, leaf subqueries containing local tables and
+	 * non-pushdownable subqueries have been replaced. We now check for
+	 * combinations of subqueries that cannot be pushed down (e.g.
+	 * <subquery on reference table> UNION <subquery on distributed table>).
+	 *
+	 * This code also runs for the top-level query, which allows us to support
+	 * top-level set operations.
+	 */
+
+	if (ShouldRecursivelyPlanSetOperation(query, context))
+	{
+		RecursivelyPlanSetOperations(query, (Node *) query->setOperations, context);
+	}
+
 	return NULL;
 }
 
@@ -450,20 +471,104 @@ ShouldRecursivelyPlanSubquery(Query *subquery)
 		return false;
 	}
 
-	/*
+	return true;
-	 * Even if we could recursively plan the subquery, we should ensure
+}
-	 * that the subquery doesn't contain any references to the outer
-	 * queries.
-	 */
-	if (ContainsReferencesToOuterQuery(subquery))
-	{
-		elog(DEBUG2, "skipping recursive planning for the subquery since it "
-					 "contains references to outer queries");
 
+
+/*
+ * ShouldRecursivelyPlanSetOperation determines whether the leaf queries of a
+ * set operations tree need to be recursively planned in order to support the
+ * query as a whole.
+ */
+static bool
+ShouldRecursivelyPlanSetOperation(Query *query, RecursivePlanningContext *context)
+{
+	PlannerRestrictionContext *filteredRestrictionContext = NULL;
+
+	SetOperationStmt *setOperations = (SetOperationStmt *) query->setOperations;
+	if (setOperations == NULL)
+	{
 		return false;
 	}
 
-	return true;
+	if (context->level == 0)
+	{
+		/*
+		 * We cannot push down top-level set operation. Recursively plan the
+		 * leaf nodes such that it becomes a router query.
+		 */
+		return true;
+	}
+
+	if (setOperations->op != SETOP_UNION)
+	{
+		/*
+		 * We can only push down UNION operaionts, plan other set operations
+		 * recursively.
+		 */
+		return true;
+	}
+
+	if (DeferErrorIfUnsupportedUnionQuery(query) != NULL)
+	{
+		/*
+		 * If at least one leaf query in the union is recurring, then all
+		 * leaf nodes need to be recurring.
+		 */
+		return true;
+	}
+
+	filteredRestrictionContext =
+		FilterPlannerRestrictionForQuery(context->plannerRestrictionContext, query);
+	if (!SafeToPushdownUnionSubquery(filteredRestrictionContext))
+	{
+		/*
+		 * The distribution column is not in the same place in all sides
+		 * of the union, meaning we cannot determine distribution column
+		 * equivalence. Recursive planning is necessary.
+		 */
+		return true;
+	}
+
+	return false;
+}
+
+
+/*
+ * RecursivelyPlanSetOperations descends into a tree of set operations
+ * (e.g. UNION, INTERSECTS) and recursively plans all leaf nodes that
+ * contain distributed tables.
+ */
+static void
+RecursivelyPlanSetOperations(Query *query, Node *node,
+							 RecursivePlanningContext *context)
+{
+	if (IsA(node, SetOperationStmt))
+	{
+		SetOperationStmt *setOperations = (SetOperationStmt *) node;
+
+		RecursivelyPlanSetOperations(query, setOperations->larg, context);
+		RecursivelyPlanSetOperations(query, setOperations->rarg, context);
+	}
+	else if (IsA(node, RangeTblRef))
+	{
+		RangeTblRef *rangeTableRef = (RangeTblRef *) node;
+		RangeTblEntry *rangeTableEntry = rt_fetch(rangeTableRef->rtindex,
+												  query->rtable);
+		Query *subquery = rangeTableEntry->subquery;
+
+		if (rangeTableEntry->rtekind == RTE_SUBQUERY &&
+			QueryContainsDistributedTableRTE(subquery))
+		{
+			RecursivelyPlanSubquery(subquery, context);
+		}
+	}
+	else
+	{
+		ereport(ERROR, (errmsg("unexpected node type (%d) while "
+							   "expecting set operations or "
+							   "range table references", nodeTag(node))));
+	}
 }
 
 
@@ -513,6 +618,13 @@ IsLocalTableRTE(Node *node)
 /*
  * RecursivelyPlanQuery recursively plans a query, replaces it with a
  * result query and returns the subplan.
+ *
+ * Before we recursively plan the given subquery, we should ensure
+ * that the subquery doesn't contain any references to the outer
+ * queries (i.e., such queries cannot be separately planned). In
+ * that case, the function doesn't recursively plan the input query
+ * and immediately returns. Later, the planner decides on what to do
+ * with the query.
  */
 static void
 RecursivelyPlanSubquery(Query *subquery, RecursivePlanningContext *planningContext)
@@ -524,6 +636,14 @@ RecursivelyPlanSubquery(Query *subquery, RecursivePlanningContext *planningConte
 	Query *resultQuery = NULL;
 	Query *debugQuery = NULL;
 
+	if (ContainsReferencesToOuterQuery(subquery))
+	{
+		elog(DEBUG2, "skipping recursive planning for the subquery since it "
+					 "contains references to outer queries");
+
+		return;
+	}
+
 	/*
 	 * Subquery will go through the standard planner, thus to properly deparse it
 	 * we keep its copy: debugQuery.

src/backend/distributed/planner/relation_restriction_equivalence.c

@@ -11,6 +11,7 @@
 #include "postgres.h"
 
 #include "distributed/distributed_planner.h"
+#include "distributed/metadata_cache.h"
 #include "distributed/multi_logical_planner.h"
 #include "distributed/multi_logical_optimizer.h"
 #include "distributed/pg_dist_partition.h"
@@ -1215,7 +1216,15 @@ AddRteRelationToAttributeEquivalenceClass(AttributeEquivalenceClass **
 {
 	AttributeEquivalenceClassMember *attributeEqMember = NULL;
 	Oid relationId = rangeTableEntry->relid;
-	Var *relationPartitionKey = DistPartitionKey(relationId);
+	Var *relationPartitionKey = NULL;
+
+	/* we don't consider local tables in the equality on columns */
+	if (!IsDistributedTable(relationId))
+	{
+		return;
+	}
+
+	relationPartitionKey = DistPartitionKey(relationId);
 
 	Assert(rangeTableEntry->rtekind == RTE_RELATION);
 

src/include/distributed/multi_logical_planner.h

@@ -191,12 +191,14 @@ extern bool SingleRelationRepartitionSubquery(Query *queryTree);
 extern DeferredErrorMessage * DeferErrorIfCannotPushdownSubquery(Query *subqueryTree,
 																 bool
 																 outerMostQueryHasLimit);
+extern DeferredErrorMessage * DeferErrorIfUnsupportedUnionQuery(Query *queryTree);
 extern PlannerRestrictionContext * FilterPlannerRestrictionForQuery(
 	PlannerRestrictionContext *plannerRestrictionContext,
 	Query *query);
 extern bool SafeToPushdownWindowFunction(Query *query, StringInfo *errorDetail);
 extern bool TargetListOnPartitionColumn(Query *query, List *targetEntryList);
 extern bool FindNodeCheckInRangeTableList(List *rtable, bool (*check)(Node *));
+extern bool QueryContainsDistributedTableRTE(Query *query);
 extern bool ContainsReadIntermediateResultFunction(Node *node);
 extern MultiNode * ParentNode(MultiNode *multiNode);
 extern MultiNode * ChildNode(MultiUnaryNode *multiNode);

src/test/regress/expected/multi_insert_select.out

@@ -721,15 +721,24 @@ FROM
 DEBUG:  Set operations are not allowed in distributed INSERT ... SELECT queries
 DEBUG:  Collecting INSERT ... SELECT results on coordinator
 ROLLBACK;
--- We do not support any set operations
+-- We do support set operations through recursive planning
+BEGIN;
+SET LOCAL client_min_messages TO DEBUG;
 INSERT INTO
   raw_events_first(user_id)
   (SELECT user_id FROM raw_events_first) INTERSECT
   (SELECT user_id FROM raw_events_first);
 DEBUG:  Set operations are not allowed in distributed INSERT ... SELECT queries
 DEBUG:  Collecting INSERT ... SELECT results on coordinator
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+DEBUG:  generating subplan 58_1 for subquery SELECT user_id FROM public.raw_events_first
-HINT:  Consider using an equality filter on the distributed table's partition column.
+DEBUG:  generating subplan 58_2 for subquery SELECT user_id FROM public.raw_events_first
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 58_3 for subquery SELECT intermediate_result.user_id FROM read_intermediate_result('58_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer) INTERSECT SELECT intermediate_result.user_id FROM read_intermediate_result('58_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)
+DEBUG:  Plan 58 query after replacing subqueries and CTEs: SELECT user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('58_3'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) citus_insert_select_subquery
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ROLLBACK;
 -- If the query is router plannable then it is executed via the coordinator
 INSERT INTO
   raw_events_first(user_id)
@@ -1078,8 +1087,8 @@ DEBUG:  join prunable for intervals [0,1073741823] and [1073741824,2147483647]
 DEBUG:  join prunable for intervals [1073741824,2147483647] and [-2147483648,-1073741825]
 DEBUG:  join prunable for intervals [1073741824,2147483647] and [-1073741824,-1]
 DEBUG:  join prunable for intervals [1073741824,2147483647] and [0,1073741823]
-DEBUG:  generating subplan 86_1 for subquery SELECT sum(raw_events_second.value_4) AS v4, sum(raw_events_first.value_1) AS v1, raw_events_second.value_3 AS id FROM public.raw_events_first, public.raw_events_second WHERE (raw_events_first.user_id = raw_events_second.user_id) GROUP BY raw_events_second.value_3
+DEBUG:  generating subplan 88_1 for subquery SELECT sum(raw_events_second.value_4) AS v4, sum(raw_events_first.value_1) AS v1, raw_events_second.value_3 AS id FROM public.raw_events_first, public.raw_events_second WHERE (raw_events_first.user_id = raw_events_second.user_id) GROUP BY raw_events_second.value_3
-DEBUG:  Plan 86 query after replacing subqueries and CTEs: SELECT id, v1, v4 FROM (SELECT intermediate_result.v4, intermediate_result.v1, intermediate_result.id FROM read_intermediate_result('86_1'::text, 'binary'::citus_copy_format) intermediate_result(v4 numeric, v1 bigint, id double precision)) foo
+DEBUG:  Plan 88 query after replacing subqueries and CTEs: SELECT id, v1, v4 FROM (SELECT intermediate_result.v4, intermediate_result.v1, intermediate_result.id FROM read_intermediate_result('88_1'::text, 'binary'::citus_copy_format) intermediate_result(v4 numeric, v1 bigint, id double precision)) foo
 DEBUG:  Creating router plan
 DEBUG:  Plan is router executable
 ERROR:  the partition column of table public.agg_events cannot be NULL
@@ -1209,8 +1218,8 @@ DEBUG:  join prunable for intervals [0,1073741823] and [1073741824,2147483647]
 DEBUG:  join prunable for intervals [1073741824,2147483647] and [-2147483648,-1073741825]
 DEBUG:  join prunable for intervals [1073741824,2147483647] and [-1073741824,-1]
 DEBUG:  join prunable for intervals [1073741824,2147483647] and [0,1073741823]
-DEBUG:  generating subplan 105_1 for subquery SELECT sum(raw_events_second.value_4) AS v4, raw_events_second.value_1 AS v1, sum(raw_events_second.user_id) AS id FROM public.raw_events_first, public.raw_events_second WHERE (raw_events_first.user_id = raw_events_second.user_id) GROUP BY raw_events_second.value_1 HAVING (sum(raw_events_second.value_4) > (10)::numeric)
+DEBUG:  generating subplan 107_1 for subquery SELECT sum(raw_events_second.value_4) AS v4, raw_events_second.value_1 AS v1, sum(raw_events_second.user_id) AS id FROM public.raw_events_first, public.raw_events_second WHERE (raw_events_first.user_id = raw_events_second.user_id) GROUP BY raw_events_second.value_1 HAVING (sum(raw_events_second.value_4) > (10)::numeric)
-DEBUG:  Plan 105 query after replacing subqueries and CTEs: SELECT f2.id FROM ((SELECT foo.id FROM (SELECT reference_table.user_id AS id FROM public.raw_events_first, public.reference_table WHERE (raw_events_first.user_id = reference_table.user_id)) foo) f JOIN (SELECT foo2.v4, foo2.v1, foo2.id FROM (SELECT intermediate_result.v4, intermediate_result.v1, intermediate_result.id FROM read_intermediate_result('105_1'::text, 'binary'::citus_copy_format) intermediate_result(v4 numeric, v1 integer, id bigint)) foo2) f2 ON ((f.id = f2.id)))
+DEBUG:  Plan 107 query after replacing subqueries and CTEs: SELECT f2.id FROM ((SELECT foo.id FROM (SELECT reference_table.user_id AS id FROM public.raw_events_first, public.reference_table WHERE (raw_events_first.user_id = reference_table.user_id)) foo) f JOIN (SELECT foo2.v4, foo2.v1, foo2.id FROM (SELECT intermediate_result.v4, intermediate_result.v1, intermediate_result.id FROM read_intermediate_result('107_1'::text, 'binary'::citus_copy_format) intermediate_result(v4 numeric, v1 integer, id bigint)) foo2) f2 ON ((f.id = f2.id)))
 -- the second part of the query is not routable since
 -- GROUP BY not on the partition column (i.e., value_1) and thus join
 -- on f.id = f2.id is not on the partition key (instead on the sum of partition key)
@@ -1251,8 +1260,8 @@ DEBUG:  join prunable for intervals [0,1073741823] and [1073741824,2147483647]
 DEBUG:  join prunable for intervals [1073741824,2147483647] and [-2147483648,-1073741825]
 DEBUG:  join prunable for intervals [1073741824,2147483647] and [-1073741824,-1]
 DEBUG:  join prunable for intervals [1073741824,2147483647] and [0,1073741823]
-DEBUG:  generating subplan 108_1 for subquery SELECT sum(raw_events_second.value_4) AS v4, raw_events_second.value_1 AS v1, sum(raw_events_second.user_id) AS id FROM public.raw_events_first, public.raw_events_second WHERE (raw_events_first.user_id = raw_events_second.user_id) GROUP BY raw_events_second.value_1 HAVING (sum(raw_events_second.value_4) > (10)::numeric)
+DEBUG:  generating subplan 110_1 for subquery SELECT sum(raw_events_second.value_4) AS v4, raw_events_second.value_1 AS v1, sum(raw_events_second.user_id) AS id FROM public.raw_events_first, public.raw_events_second WHERE (raw_events_first.user_id = raw_events_second.user_id) GROUP BY raw_events_second.value_1 HAVING (sum(raw_events_second.value_4) > (10)::numeric)
-DEBUG:  Plan 108 query after replacing subqueries and CTEs: SELECT f.id FROM ((SELECT foo.id FROM (SELECT raw_events_first.user_id AS id FROM public.raw_events_first, public.reference_table WHERE (raw_events_first.user_id = reference_table.user_id)) foo) f JOIN (SELECT foo2.v4, foo2.v1, foo2.id FROM (SELECT intermediate_result.v4, intermediate_result.v1, intermediate_result.id FROM read_intermediate_result('108_1'::text, 'binary'::citus_copy_format) intermediate_result(v4 numeric, v1 integer, id bigint)) foo2) f2 ON ((f.id = f2.id)))
+DEBUG:  Plan 110 query after replacing subqueries and CTEs: SELECT f.id FROM ((SELECT foo.id FROM (SELECT raw_events_first.user_id AS id FROM public.raw_events_first, public.reference_table WHERE (raw_events_first.user_id = reference_table.user_id)) foo) f JOIN (SELECT foo2.v4, foo2.v1, foo2.id FROM (SELECT intermediate_result.v4, intermediate_result.v1, intermediate_result.id FROM read_intermediate_result('110_1'::text, 'binary'::citus_copy_format) intermediate_result(v4 numeric, v1 integer, id bigint)) foo2) f2 ON ((f.id = f2.id)))
 -- cannot pushdown the query since the JOIN is not equi JOIN
 INSERT INTO agg_events
             (user_id, value_4_agg)

src/test/regress/expected/multi_insert_select_non_pushable_queries.out

@@ -118,7 +118,8 @@ FROM (
   ) t2 ON (t1.user_id = t2.user_id)
   GROUP BY  t1.user_id, hasdone_event
 ) t GROUP BY user_id, hasdone_event;
-ERROR:  complex joins are only supported when all distributed tables are joined on their distribution columns with equal operator
+ERROR:  the query contains a join that requires repartitioning
+HINT:  Set citus.enable_repartition_joins to on to enable repartitioning
 -- the LEFT JOIN conditon is not on the partition column (i.e., is it part_key divided by 2)
 INSERT INTO agg_results_third (user_id, value_1_agg, value_2_agg )
 SELECT user_id, sum(array_length(events_table, 1)), length(hasdone_event)

src/test/regress/expected/multi_mx_router_planner.out

@@ -792,21 +792,36 @@ DEBUG:  Plan is router executable
  az
 (4 rows)
 
--- union queries are not supported if not router plannable
+-- union queries are supported through recursive planning
--- there is an inconsistency on shard pruning between
+SET client_min_messages TO DEBUG1;
--- ubuntu/mac disabling log messages for this queries only
-SET client_min_messages to 'NOTICE';
 (SELECT * FROM articles_hash_mx WHERE author_id = 1)
 UNION
-(SELECT * FROM articles_hash_mx WHERE author_id = 2);
+(SELECT * FROM articles_hash_mx WHERE author_id = 2)
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ORDER BY 1,2;
-HINT:  Consider using an equality filter on the distributed table's partition column.
+DEBUG:  generating subplan 108_1 for subquery SELECT id, author_id, title, word_count FROM public.articles_hash_mx WHERE (author_id = 1)
+DEBUG:  generating subplan 108_2 for subquery SELECT id, author_id, title, word_count FROM public.articles_hash_mx WHERE (author_id = 2)
+DEBUG:  Plan 108 query after replacing subqueries and CTEs: SELECT intermediate_result.id, intermediate_result.author_id, intermediate_result.title, intermediate_result.word_count FROM read_intermediate_result('108_1'::text, 'binary'::citus_copy_format) intermediate_result(id bigint, author_id bigint, title character varying(20), word_count integer) UNION SELECT intermediate_result.id, intermediate_result.author_id, intermediate_result.title, intermediate_result.word_count FROM read_intermediate_result('108_2'::text, 'binary'::citus_copy_format) intermediate_result(id bigint, author_id bigint, title character varying(20), word_count integer) ORDER BY 1, 2
+ id | author_id |    title     | word_count 
+----+-----------+--------------+------------
+  1 |         1 | arsenous     |       9572
+  2 |         2 | abducing     |      13642
+ 11 |         1 | alamo        |       1347
+ 12 |         2 | archiblast   |      18185
+ 21 |         1 | arcading     |       5890
+ 22 |         2 | antipope     |       2728
+ 31 |         1 | athwartships |       7271
+ 32 |         2 | amazon       |      11342
+ 41 |         1 | aznavour     |      11814
+ 42 |         2 | ausable      |      15885
+(10 rows)
+
 SELECT * FROM (
 	(SELECT * FROM articles_hash_mx WHERE author_id = 1)
 	UNION
 	(SELECT * FROM articles_hash_mx WHERE author_id = 2)) uu
 ORDER BY 1, 2
 LIMIT 5;
+DEBUG:  push down of limit count: 5
  id | author_id |   title    | word_count 
 ----+-----------+------------+------------
   1 |         1 | arsenous   |       9572

src/test/regress/expected/multi_router_planner.out

@@ -906,15 +906,35 @@ DEBUG:  Plan is router executable
  az
 (4 rows)
 
--- top-level union queries are not supported if not router plannable
+-- top-level union queries are supported through recursive planning
--- there is an inconsistency on shard pruning between
--- ubuntu/mac disabling log messages for this queries only
 SET client_min_messages to 'NOTICE';
-(SELECT * FROM articles_hash WHERE author_id = 1)
+(
+  (SELECT * FROM articles_hash WHERE author_id = 1)
+  UNION
+  (SELECT * FROM articles_hash WHERE author_id = 3)
+)
 UNION
-(SELECT * FROM articles_hash WHERE author_id = 2);
+(SELECT * FROM articles_hash WHERE author_id = 2)
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ORDER BY 1,2,3;
-HINT:  Consider using an equality filter on the distributed table's partition column.
+ id | author_id |    title     | word_count 
+----+-----------+--------------+------------
+  1 |         1 | arsenous     |       9572
+  2 |         2 | abducing     |      13642
+  3 |         3 | asternal     |      10480
+ 11 |         1 | alamo        |       1347
+ 12 |         2 | archiblast   |      18185
+ 13 |         3 | aseyev       |       2255
+ 21 |         1 | arcading     |       5890
+ 22 |         2 | antipope     |       2728
+ 23 |         3 | abhorring    |       6799
+ 31 |         1 | athwartships |       7271
+ 32 |         2 | amazon       |      11342
+ 33 |         3 | autochrome   |       8180
+ 41 |         1 | aznavour     |      11814
+ 42 |         2 | ausable      |      15885
+ 43 |         3 | affixal      |      12723
+(15 rows)
+
 -- unions in subqueries are supported with subquery pushdown
 SELECT * FROM (
 	(SELECT * FROM articles_hash WHERE author_id = 1)

src/test/regress/expected/multi_simple_queries.out

@@ -167,11 +167,24 @@ SELECT author_id, sum(word_count) AS corpus_size FROM articles
          8 |       55410
 (3 rows)
 
--- UNION/INTERSECT queries are unsupported if on multiple shards
+-- UNION/INTERSECT queries are supported if on multiple shards
 SELECT * FROM articles WHERE author_id = 10 UNION
-SELECT * FROM articles WHERE author_id = 2; 
+SELECT * FROM articles WHERE author_id = 2
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ORDER BY 1,2,3;
-HINT:  Consider using an equality filter on the distributed table's partition column.
+ id | author_id |   title    | word_count 
+----+-----------+------------+------------
+  2 |         2 | abducing   |      13642
+ 10 |        10 | aggrandize |      17277
+ 12 |         2 | archiblast |      18185
+ 20 |        10 | absentness |       1820
+ 22 |         2 | antipope   |       2728
+ 30 |        10 | andelee    |       6363
+ 32 |         2 | amazon     |      11342
+ 40 |        10 | attemper   |      14976
+ 42 |         2 | ausable    |      15885
+ 50 |        10 | anjanette  |      19519
+(10 rows)
+
 -- queries using CTEs are supported
 WITH long_names AS ( SELECT id FROM authors WHERE char_length(name) > 15 )
 SELECT title FROM articles ORDER BY 1 LIMIT 5;

src/test/regress/expected/multi_simple_queries_0.out

@@ -167,11 +167,24 @@ SELECT author_id, sum(word_count) AS corpus_size FROM articles
          8 |       55410
 (3 rows)
 
--- UNION/INTERSECT queries are unsupported if on multiple shards
+-- UNION/INTERSECT queries are supported if on multiple shards
 SELECT * FROM articles WHERE author_id = 10 UNION
-SELECT * FROM articles WHERE author_id = 2; 
+SELECT * FROM articles WHERE author_id = 2
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ORDER BY 1,2,3;
-HINT:  Consider using an equality filter on the distributed table's partition column.
+ id | author_id |   title    | word_count 
+----+-----------+------------+------------
+  2 |         2 | abducing   |      13642
+ 10 |        10 | aggrandize |      17277
+ 12 |         2 | archiblast |      18185
+ 20 |        10 | absentness |       1820
+ 22 |         2 | antipope   |       2728
+ 30 |        10 | andelee    |       6363
+ 32 |         2 | amazon     |      11342
+ 40 |        10 | attemper   |      14976
+ 42 |         2 | ausable    |      15885
+ 50 |        10 | anjanette  |      19519
+(10 rows)
+
 -- queries using CTEs are supported
 WITH long_names AS ( SELECT id FROM authors WHERE char_length(name) > 15 )
 SELECT title FROM articles ORDER BY 1 LIMIT 5;

src/test/regress/expected/multi_subquery.out

@@ -3,7 +3,6 @@
 --
 -- no need to set shardid sequence given that we're not creating any shards
 SET citus.next_shard_id TO 570032;
-SET citus.enable_router_execution TO FALSE;
 -- Check that we error out if shard min/max values are not exactly same.
 SELECT
 	avg(unit_price)
@@ -39,7 +38,11 @@ FROM
 		lineitem_subquery
 	GROUP BY
 		l_suppkey) AS order_counts;
-ERROR:  cannot handle complex subqueries when the router executor is disabled
+        avg         
+--------------------
+ 1.7199369356456930
+(1 row)
+
 -- Check that we error out if join is not on partition columns.
 SELECT
 	avg(unit_price)
@@ -76,22 +79,45 @@ SELECT count(*) FROM (
      0
 (1 row)
 
--- Check that we error out if there is non relation subqueries
+SET client_min_messages TO DEBUG;
+-- If there is non relation subqueries then we recursively plan
 SELECT count(*) FROM
 (
    (SELECT l_orderkey FROM lineitem_subquery) UNION ALL
    (SELECT 1::bigint)
 ) b;
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+DEBUG:  generating subplan 7_1 for subquery SELECT l_orderkey FROM public.lineitem_subquery
--- Check that we error out if queries in union do not include partition columns.
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 7_2 for subquery SELECT intermediate_result.l_orderkey FROM read_intermediate_result('7_1'::text, 'binary'::citus_copy_format) intermediate_result(l_orderkey bigint) UNION ALL SELECT (1)::bigint AS int8
+DEBUG:  Plan 7 query after replacing subqueries and CTEs: SELECT count(*) AS count FROM (SELECT intermediate_result.l_orderkey FROM read_intermediate_result('7_2'::text, 'binary'::citus_copy_format) intermediate_result(l_orderkey bigint)) b
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ count 
+-------
+ 12001
+(1 row)
+
+-- If queries in union do not include partition columns then we recursively plan
 SELECT count(*) FROM
 (
    (SELECT l_orderkey FROM lineitem_subquery) UNION
    (SELECT l_partkey FROM lineitem_subquery)
 ) b;
-ERROR:  cannot pushdown the subquery since not all subqueries in the UNION have the partition column in the same position
+DEBUG:  generating subplan 10_1 for subquery SELECT l_orderkey FROM public.lineitem_subquery
-DETAIL:  Each leaf query of the UNION should return the partition column in the same position and all joins must be on the partition column
+DEBUG:  generating subplan 10_2 for subquery SELECT l_partkey FROM public.lineitem_subquery
--- Check that we run union queries if partition column is selected.
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 10_3 for subquery SELECT intermediate_result.l_orderkey FROM read_intermediate_result('10_1'::text, 'binary'::citus_copy_format) intermediate_result(l_orderkey bigint) UNION SELECT intermediate_result.l_partkey FROM read_intermediate_result('10_2'::text, 'binary'::citus_copy_format) intermediate_result(l_partkey integer)
+DEBUG:  Plan 10 query after replacing subqueries and CTEs: SELECT count(*) AS count FROM (SELECT intermediate_result.l_orderkey FROM read_intermediate_result('10_3'::text, 'binary'::citus_copy_format) intermediate_result(l_orderkey bigint)) b
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ count 
+-------
+ 14496
+(1 row)
+
+-- Check that we push down union queries if partition column is selected (no DEBUG messages)
 SELECT count(*) FROM
 (
    (SELECT l_orderkey FROM lineitem_subquery) UNION
@@ -102,6 +128,7 @@ SELECT count(*) FROM
   2985
 (1 row)
 
+RESET client_min_messages;
 -- we'd error out if inner query has Limit but subquery_pushdown is not set
 -- but we recursively plan the query
 SELECT
@@ -692,6 +719,8 @@ SELECT master_create_worker_shards('subquery_pruning_varchar_test_table', 4, 1);
  
 (1 row)
 
+-- temporarily disable router executor to test pruning behaviour of subquery pushdown
+SET citus.enable_router_execution TO off;
 SET client_min_messages TO DEBUG2;
 SELECT * FROM
 	(SELECT count(*) FROM subquery_pruning_varchar_test_table WHERE a = 'onder' GROUP BY a)
@@ -747,6 +776,7 @@ AS foo;
 (0 rows)
 
 DROP TABLE subquery_pruning_varchar_test_table;
+RESET citus.enable_router_execution;
 -- Simple join subquery pushdown
 SELECT
 	avg(array_length(events, 1)) AS event_average
@@ -1001,4 +1031,3 @@ $f$);
 DROP FUNCTION run_command_on_master_and_workers(p_sql text);
 SET client_min_messages TO DEFAULT;
 SET citus.subquery_pushdown to OFF;
-SET citus.enable_router_execution TO 'true';

src/test/regress/expected/multi_subquery_complex_queries.out

@@ -7,7 +7,6 @@
 -- SET citus.next_shard_id TO 1400000;
 ALTER SEQUENCE pg_catalog.pg_dist_jobid_seq RESTART 1400000;
  
-SET citus.enable_router_execution TO FALSE;
  -- 
  -- UNIONs and JOINs mixed
  --
@@ -144,7 +143,7 @@ ORDER BY
      3 |            268
 (4 rows)
 
--- not supported since events_subquery_2 doesn't have partition key on the target list
+-- supported through recursive planning since events_subquery_2 doesn't have partition key on the target list
 -- within the shuffled target list
 SELECT ("final_query"."event_types") as types, count(*) AS sumOfEventType
 FROM
@@ -202,8 +201,15 @@ GROUP BY
   types
 ORDER BY 
   types;
-ERROR:  complex joins are only supported when all distributed tables are joined on their distribution columns with equal operator
+ types | sumofeventtype 
--- not supported since events_subquery_2 doesn't have partition key on the target list
+-------+----------------
+     0 |            449
+     1 |            234
+     2 |             75
+     3 |            268
+(4 rows)
+
+-- supported through recursive planning since events_subquery_2 doesn't have partition key on the target list
 SELECT ("final_query"."event_types") as types, count(*) AS sumOfEventType
 FROM
   ( SELECT *, random()
@@ -260,7 +266,14 @@ GROUP BY
   types
 ORDER BY 
   types;
-ERROR:  complex joins are only supported when all distributed tables are joined on their distribution columns with equal operator
+ types | sumofeventtype 
+-------+----------------
+     0 |            449
+     1 |            369
+     2 |             75
+     3 |            268
+(4 rows)
+
 -- we can support arbitrary subqueries within UNIONs
 SELECT ("final_query"."event_types") as types, count(*) AS sumOfEventType
 FROM
@@ -749,7 +762,7 @@ ORDER BY types;
      3 |            268
 (4 rows)
 
--- not supported since subquery 3 does not have partition key
+-- supported through recursive planning since subquery 3 does not have partition key
 SELECT ("final_query"."event_types") as types, count(*) AS sumOfEventType
 FROM
   ( SELECT *, random()
@@ -800,8 +813,15 @@ INNER JOIN
       WHERE value_1 > 0 and value_1 < 4) AS t ON (t.user_id = q.user_id)) as final_query
 GROUP BY types
 ORDER BY types;
-ERROR:  complex joins are only supported when all distributed tables are joined on their distribution columns with equal operator
+ types | sumofeventtype 
--- not supported since events_subquery_4 does not have partition key on the 
+-------+----------------
+     0 |            449
+     1 |            433
+     2 |             62
+     3 |            268
+(4 rows)
+
+-- supported through recursive planning since events_subquery_4 does not have partition key on the 
 -- target list
 SELECT ("final_query"."event_types") as types, count(*) AS sumOfEventType
 FROM
@@ -857,7 +877,14 @@ INNER JOIN
 ON (t.user_id = q.user_id)) as final_query
 GROUP BY types
 ORDER BY types;
-ERROR:  complex joins are only supported when all distributed tables are joined on their distribution columns with equal operator
+ types | sumofeventtype 
+-------+----------------
+     0 |            449
+     1 |            433
+     2 |             75
+     3 |            124
+(4 rows)
+
 -- union all with inner and left joins
 SELECT user_id, count(*) as cnt
 FROM
@@ -2263,12 +2290,16 @@ GROUP BY
   types
 ORDER BY 
   types;
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ types | sumofeventtype 
-HINT:  Consider using an equality filter on the distributed table's partition column.
+-------+----------------
--- not supported due to offset
+     0 |            449
+     1 |            433
+(2 rows)
+
+-- supported through recursive planning
 SELECT ("final_query"."event_types") as types, count(*) AS sumOfEventType
 FROM
-  ( SELECT *, random()
+  ( SELECT *
    FROM
      ( SELECT "t"."user_id", "t"."time", unnest("t"."collected_events") AS "event_types"
       FROM
@@ -2312,7 +2343,7 @@ FROM
                      FROM 
                       events_table as "events"
                      WHERE 
-                      event_type IN (4, 5)) events_subquery_4) OFFSET 3) t1
+                      event_type IN (4, 5)) events_subquery_4) ORDER BY 1, 2 OFFSET 3) t1
          GROUP BY "t1"."user_id") AS t) "q" 
 INNER JOIN
      (SELECT 
@@ -2326,8 +2357,14 @@ GROUP BY
   types
 ORDER BY 
   types;
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ types | sumofeventtype 
-HINT:  Consider using an equality filter on the distributed table's partition column.
+-------+----------------
+     0 |            449
+     1 |            425
+     2 |             75
+     3 |            251
+(4 rows)
+
 -- not supported due to non relation rte
 SELECT ("final_query"."event_types") as types, count(*) AS sumOfEventType
 FROM
@@ -2386,8 +2423,14 @@ GROUP BY
   types
 ORDER BY 
   types;
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ types | sumofeventtype 
-HINT:  Consider using an equality filter on the distributed table's partition column.
+-------+----------------
+     0 |            449
+     1 |            433
+     2 |             75
+     3 |              4
+(4 rows)
+
 -- similar to the above, but constant rte is on the right side of the query
 SELECT ("final_query"."event_types") as types, count(*) AS sumOfEventType
 FROM
@@ -2435,12 +2478,17 @@ FROM
                     ) events_subquery_4)) t1
          GROUP BY "t1"."user_id") AS t) "q" 
 INNER JOIN
-     (SELECT random()::int as user_id) AS t 
+     (SELECT 1 as user_id) AS t 
     ON (t.user_id = q.user_id)) as final_query
 GROUP BY 
   types
 ORDER BY 
   types;
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ types | sumofeventtype 
-HINT:  Consider using an equality filter on the distributed table's partition column.
+-------+----------------
-SET citus.enable_router_execution TO TRUE;
+     0 |              4
+     1 |              8
+     2 |              1
+     3 |              1
+(4 rows)
+

src/test/regress/expected/multi_subquery_complex_reference_clause.out

@@ -6,7 +6,6 @@
 -- We don't need shard id sequence here, so commented out to prevent conflicts with concurrent tests
 -- SET citus.next_shard_id TO 1400000;
 ALTER SEQUENCE pg_catalog.pg_dist_jobid_seq RESTART 1400000;
-SET citus.enable_router_execution TO FALSE;
 CREATE TABLE user_buy_test_table(user_id int, item_id int, buy_count int);
 SELECT create_distributed_table('user_buy_test_table', 'user_id');
  create_distributed_table 
@@ -261,23 +260,52 @@ SELECT count(*) FROM user_buy_test_table RIGHT JOIN (SELECT * FROM generate_seri
 ON user_buy_test_table.item_id = users_ref_test_table.id;
 ERROR:  cannot pushdown the subquery
 DETAIL:  There exist a table function in the outer part of the outer join
--- volatile functions cannot be used as table expressions
+-- volatile functions can be used as table expressions through recursive planning
+SET client_min_messages TO DEBUG;
 SELECT count(*) FROM
   (SELECT random() FROM user_buy_test_table JOIN random() AS users_ref_test_table(id)
   ON user_buy_test_table.item_id > users_ref_test_table.id) subquery_1;
-ERROR:  cannot handle complex subqueries when the router executor is disabled
+DEBUG:  generating subplan 30_1 for subquery SELECT random() AS random FROM (public.user_buy_test_table JOIN random() users_ref_test_table(id) ON (((user_buy_test_table.item_id)::double precision > users_ref_test_table.id)))
--- cannot sneak in a volatile function as a parameter
+DEBUG:  Plan 30 query after replacing subqueries and CTEs: SELECT count(*) AS count FROM (SELECT intermediate_result.random FROM read_intermediate_result('30_1'::text, 'binary'::citus_copy_format) intermediate_result(random double precision)) subquery_1
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ count 
+-------
+     4
+(1 row)
+
+-- can sneak in a volatile function as a parameter
 SELECT count(*) FROM
-  (SELECT random() FROM user_buy_test_table JOIN generate_series(random()::int,10) AS users_ref_test_table(id)
+  (SELECT item_id FROM user_buy_test_table JOIN generate_series(random()::int,10) AS users_ref_test_table(id)
-  ON user_buy_test_table.item_id > users_ref_test_table.id) subquery_1;
+  ON user_buy_test_table.item_id > users_ref_test_table.id) subquery_1
-ERROR:  cannot handle complex subqueries when the router executor is disabled
+WHERE item_id = 6;
--- cannot perform a union with table function
+DEBUG:  generating subplan 32_1 for subquery SELECT user_buy_test_table.item_id FROM (public.user_buy_test_table JOIN generate_series((random())::integer, 10) users_ref_test_table(id) ON ((user_buy_test_table.item_id > users_ref_test_table.id)))
+DEBUG:  Plan 32 query after replacing subqueries and CTEs: SELECT count(*) AS count FROM (SELECT intermediate_result.item_id FROM read_intermediate_result('32_1'::text, 'binary'::citus_copy_format) intermediate_result(item_id integer)) subquery_1 WHERE (item_id = 6)
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ count 
+-------
+     0
+(1 row)
+
+-- can perform a union with table function through recursive planning
 SELECT count(*) FROM
   (SELECT user_id FROM user_buy_test_table
    UNION ALL
    SELECT id FROM generate_series(1,10) AS users_ref_test_table(id)) subquery_1;
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+DEBUG:  generating subplan 34_1 for subquery SELECT user_id FROM public.user_buy_test_table
-HINT:  Consider using an equality filter on the distributed table's partition column.
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 34_2 for subquery SELECT intermediate_result.user_id FROM read_intermediate_result('34_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer) UNION ALL SELECT users_ref_test_table.id FROM generate_series(1, 10) users_ref_test_table(id)
+DEBUG:  Plan 34 query after replacing subqueries and CTEs: SELECT count(*) AS count FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('34_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) subquery_1
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ count 
+-------
+    14
+(1 row)
+
+RESET client_min_messages;
 -- subquery without FROM can be the inner relationship in a join
 SELECT count(*) FROM
   (SELECT random() FROM user_buy_test_table JOIN (SELECT 4 AS id) users_ref_test_table
@@ -308,13 +336,16 @@ SELECT count(*) FROM user_buy_test_table RIGHT JOIN (SELECT 5 AS id) users_ref_t
 ON user_buy_test_table.item_id = users_ref_test_table.id;
 ERROR:  cannot pushdown the subquery
 DETAIL:  There exist a subquery without FROM in the outer part of the outer join
--- cannot perform a union with subquery without FROM
+-- can perform a union with subquery without FROM
 SELECT count(*) FROM
   (SELECT user_id FROM user_buy_test_table
    UNION ALL
    SELECT id FROM (SELECT 5 AS id) users_ref_test_table) subquery_1;
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ count 
-HINT:  Consider using an equality filter on the distributed table's partition column.
+-------
+     5
+(1 row)
+
 -- should be able to pushdown since reference table is in the
 -- inner part of the left join
 SELECT
@@ -983,10 +1014,18 @@ INNER JOIN
         value_1 > 2 and value_1 < 4) AS t
     ON (t.user_id = q.user_id)) as final_query
 ORDER BY
-  types;
+  types
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+LIMIT 5;
-HINT:  Consider using an equality filter on the distributed table's partition column.
+ types 
-  -- reference table exist in the subquery of union, should error out
+-------
+     0
+     0
+     0
+     0
+     0
+(5 rows)
+
+  -- reference table exist in the subquery of union
 SELECT ("final_query"."event_types") as types, count(*) AS sumOfEventType
 FROM
   ( SELECT
@@ -1057,8 +1096,13 @@ GROUP BY
   types
 ORDER BY
   types;
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ types | sumofeventtype 
-HINT:  Consider using an equality filter on the distributed table's partition column.
+-------+----------------
+     0 |            217
+     2 |            191
+     3 |             31
+(3 rows)
+
 --
 -- Should error out with UNION ALL Queries on reference tables
 --
@@ -1112,8 +1156,14 @@ INNER JOIN
       WHERE value_1 > 2 and value_1 < 4) AS t ON (t.user_id = q.user_id)) as final_query
 GROUP BY types
 ORDER BY types;
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ types | sumofeventtype 
-HINT:  Consider using an equality filter on the distributed table's partition column.
+-------+----------------
+     0 |            191
+     1 |            191
+     2 |             31
+     3 |            120
+(4 rows)
+
 -- just a sanity check that we don't allow this if the reference table is on the
 -- left part of the left join
 SELECT count(*) FROM
@@ -1201,15 +1251,25 @@ SELECT foo.user_id FROM
 (0 rows)
 
 -- not pushdownable since group by is on the reference table column
--- recursively planned, but hits unsupported clause type error on the top level query
+-- recursively planned
 SELECT foo.user_id FROM
 (
   SELECT r.user_id, random() FROM users_table m JOIN events_reference_table r ON int4eq(m.user_id, r.user_id)
   GROUP BY r.user_id
-) as foo;
+) as foo
-ERROR:  cannot handle complex subqueries when the router executor is disabled
+ORDER BY 1 DESC;
+ user_id 
+---------
+       6
+       5
+       4
+       3
+       2
+       1
+(6 rows)
+
 -- not pushdownable since the group by contains at least one distributed table
--- recursively planned, but hits unsupported clause type error on the top level query
+-- recursively planned
 SELECT foo.user_id FROM
 (
   SELECT r.user_id, random() FROM users_table m JOIN events_reference_table r ON int4eq(m.user_id, r.user_id)
@@ -1224,18 +1284,38 @@ ORDER BY 1 LIMIT 3;
 (3 rows)
 
 -- not pushdownable since distinct is on the reference table column
--- recursively planned, but hits unsupported clause type error on the top level query
+-- recursively planned
 SELECT foo.user_id FROM
 (
   SELECT DISTINCT r.user_id, random() FROM users_table m JOIN events_reference_table r ON int4eq(m.user_id, r.user_id)
-) as foo;
+) as foo
-ERROR:  cannot handle complex subqueries when the router executor is disabled
+ORDER BY 1 DESC
+LIMIT 5;
+ user_id 
+---------
+       6
+       6
+       6
+       6
+       6
+(5 rows)
+
 -- not supported since distinct on is on the reference table column
+-- but recursively planned
 SELECT foo.user_id FROM
 (
   SELECT DISTINCT ON(r.user_id) r.user_id, random() FROM users_table m JOIN events_reference_table r ON int4eq(m.user_id, r.user_id)
 ) as foo;
-ERROR:  cannot handle complex subqueries when the router executor is disabled
+ user_id 
+---------
+       1
+       2
+       3
+       4
+       5
+       6
+(6 rows)
+
 -- supported since the distinct on contains at least one distributed table
 SELECT foo.user_id FROM
 (
@@ -1313,20 +1393,36 @@ SELECT * FROM
 (
   SELECT DISTINCT users_reference_table.user_id FROM users_reference_table, events_table WHERE users_reference_table.user_id = events_table.value_4
 ) as foo;
-ERROR:  cannot handle complex subqueries when the router executor is disabled
+ user_id 
+---------
+(0 rows)
+
 SELECT * FROM
 (
   SELECT users_reference_table.user_id FROM users_reference_table, events_table WHERE users_reference_table.user_id = events_table.value_4
   GROUP BY 1
 ) as foo;
-ERROR:  cannot handle complex subqueries when the router executor is disabled
+ user_id 
+---------
+(0 rows)
+
 -- similiar to the above examples, this time there is a subquery 
 -- whose output is not in the DISTINCT clause
 SELECT * FROM
 (
   SELECT DISTINCT users_reference_table.user_id FROM users_reference_table, (SELECT user_id, random() FROM events_table) as us_events WHERE users_reference_table.user_id = us_events.user_id
-) as foo;
+) as foo
-ERROR:  cannot handle complex subqueries when the router executor is disabled
+ORDER BY 1;
+ user_id 
+---------
+       1
+       2
+       3
+       4
+       5
+       6
+(6 rows)
+
 -- the following query is safe to push down since the DISTINCT clause include distribution column
 SELECT * FROM
 (
@@ -1357,7 +1453,14 @@ SELECT * FROM
 ) as foo 
 ORDER BY 1 DESC 
 LIMIT 4;
-ERROR:  cannot handle complex subqueries when the router executor is disabled
+ user_id | value_4 
+---------+---------
+       6 |        
+       5 |        
+       4 |        
+       3 |        
+(4 rows)
+
 -- test the read_intermediate_result() for GROUP BYs
 BEGIN;
  

src/test/regress/expected/multi_subquery_in_where_clause.out

@@ -534,7 +534,8 @@ WHERE
 GROUP BY user_id
 HAVING count(*) > 1 AND sum(value_2) > 29
 ORDER BY 1;
-ERROR:  complex joins are only supported when all distributed tables are joined on their distribution columns with equal operator
+ERROR:  cannot pushdown the subquery
+DETAIL:  Complex subqueries and CTEs cannot be in the outer part of the outer join
 -- NOT EXISTS query has non-equi join
 SELECT user_id, array_length(events_table, 1)
 FROM (

src/test/regress/expected/multi_subquery_union.out

@@ -4,7 +4,6 @@
 -- the tables that are used depends to multi_insert_select_behavioral_analytics_create_table.sql
 -- We don't need shard id sequence here, so commented out to prevent conflicts with concurrent tests
 -- SET citus.next_shard_id TO 1400000;
-SET citus.enable_router_execution TO false;
 -- a very simple union query
 SELECT user_id, counter
 FROM (
@@ -47,8 +46,15 @@ FROM (
 ) user_id 
 ORDER BY 2 DESC,1
 LIMIT 5;
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ user_id | counter 
-HINT:  Consider using an equality filter on the distributed table's partition column.
+---------+---------
+       2 |       5
+       3 |       5
+       4 |       5
+       1 |       4
+       2 |       4
+(5 rows)
+
 -- the same query with union all
 SELECT user_id, counter
 FROM (
@@ -76,8 +82,15 @@ FROM (
 ) user_id 
 ORDER BY 2 DESC,1
 LIMIT 5;
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ user_id | counter 
-HINT:  Consider using an equality filter on the distributed table's partition column.
+---------+---------
+       2 |       5
+       2 |       5
+       3 |       5
+       3 |       5
+       4 |       5
+(5 rows)
+
 -- the same query with group by
 SELECT user_id, sum(counter) 
 FROM (
@@ -212,8 +225,14 @@ FROM (
     SELECT user_id, sum(value_2) AS counter FROM users_table where value_1 < 5 and value_1 < 6 GROUP BY user_id HAVING sum(value_2) > 25
 ) user_id 
 GROUP BY user_id ORDER BY 1 DESC LIMIT 5;
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ sum 
-HINT:  Consider using an equality filter on the distributed table's partition column.
+-----
+ 135
+  87
+  85
+  69
+(4 rows)
+
 -- similar query as above, with UNION ALL
 SELECT sum(counter) 
 FROM (
@@ -329,8 +348,15 @@ FROM (
             user_id)) AS ftop 
 ORDER BY 2 DESC, 1 DESC 
 LIMIT 5;
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ user_id | sum 
-HINT:  Consider using an equality filter on the distributed table's partition column.
+---------+-----
+       2 | 107
+       3 | 101
+       5 |  94
+       4 |  91
+       1 |  62
+(5 rows)
+
 -- top level unions are wrapped into top level aggregations
 SELECT ("final_query"."event_types") as types, count(*) AS sumOfEventType
 FROM
@@ -597,8 +623,11 @@ FROM
     UNION ALL
   (SELECT user_id FROM events_reference_table)
 ) b;
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ count 
-HINT:  Consider using an equality filter on the distributed table's partition column.
+-------
+   202
+(1 row)
+
 -- similar query without top level agg
 SELECT 
   user_id
@@ -738,19 +767,27 @@ LIMIT 5;
 (5 rows)
 
 -- now lets also have some unsupported queries
--- group by is not on the partition key
+-- group by is not on the partition key, supported through recursive planning
--- but we can still recursively plan it, though that is not suffient for pushdown
--- of the whole query
 SELECT user_id, sum(counter) 
 FROM (
     SELECT user_id, sum(value_2) AS counter FROM events_table GROUP BY user_id
       UNION
     SELECT value_1 as user_id, sum(value_2) AS counter FROM users_table GROUP BY value_1
 ) user_id 
-GROUP BY user_id;
+GROUP BY user_id
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ORDER BY 1,2;
-HINT:  Consider using an equality filter on the distributed table's partition column.
+ user_id | sum 
--- partition key is not selected
+---------+-----
+       0 |  31
+       1 |  76
+       2 |  99
+       3 | 119
+       4 |  94
+       5 |  57
+       6 |  22
+(7 rows)
+
+-- partition key is not selected, supported through recursive planning
 SELECT sum(counter) 
 FROM (
     SELECT user_id, sum(value_2) AS counter FROM users_table where value_1 < 1 GROUP BY user_id HAVING sum(value_2) > 25
@@ -764,9 +801,16 @@ FROM (
     SELECT 2 * user_id, sum(value_2) AS counter FROM users_table where value_1 < 5 and value_1 < 6 GROUP BY user_id HAVING sum(value_2) > 25
 ) user_id 
 GROUP BY user_id ORDER BY 1 DESC LIMIT 5;
-ERROR:  cannot pushdown the subquery since not all subqueries in the UNION have the partition column in the same position
+ sum 
-DETAIL:  Each leaf query of the UNION should return the partition column in the same position and all joins must be on the partition column
+-----
--- excepts within unions are not supported
+  80
+  76
+  55
+  50
+  43
+(5 rows)
+
+-- excepts within unions are supported through recursive planning
 SELECT * FROM
 (
 (
@@ -787,9 +831,24 @@ UNION
       SELECT user_id, sum(value_2) AS counter FROM events_table GROUP BY user_id
 ) user_id_2
   GROUP BY user_id)
-) as ftop;
+) as ftop
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ORDER BY 1,2;
-HINT:  Consider using an equality filter on the distributed table's partition column.
+ user_id | sum 
+---------+-----
+       1 |  20
+       1 |  62
+       2 |  50
+       2 | 107
+       3 |  55
+       3 | 101
+       4 |  50
+       4 |  91
+       5 |  63
+       5 |  94
+       6 |  21
+       6 |  43
+(12 rows)
+
 -- non-equi join are not supported since there is no equivalence between the partition column
 SELECT user_id, sum(counter) 
 FROM (
@@ -798,8 +857,7 @@ FROM (
     SELECT events_table.user_id, sum(events_table.value_2) AS counter FROM events_table, users_table WHERE users_table.user_id > events_table.user_id GROUP BY 1
 ) user_id 
 GROUP BY user_id;
-ERROR:  cannot pushdown the subquery since not all subqueries in the UNION have the partition column in the same position
+ERROR:  complex joins are only supported when all distributed tables are joined on their distribution columns with equal operator
-DETAIL:  Each leaf query of the UNION should return the partition column in the same position and all joins must be on the partition column
 -- non-equi join also not supported for UNION ALL
 SELECT user_id, sum(counter)
 FROM (
@@ -808,8 +866,7 @@ FROM (
     SELECT events_table.user_id, sum(events_table.value_2) AS counter FROM events_table, users_table WHERE users_table.user_id > events_table.user_id GROUP BY 1
 ) user_id 
 GROUP BY user_id;
-ERROR:  cannot pushdown the subquery since not all subqueries in the UNION have the partition column in the same position
+ERROR:  complex joins are only supported when all distributed tables are joined on their distribution columns with equal operator
-DETAIL:  Each leaf query of the UNION should return the partition column in the same position and all joins must be on the partition column
 -- joins inside unions are supported -- slightly more comlex than the above
 SELECT * FROM
 (
@@ -942,11 +999,18 @@ SELECT user_id, sum(counter)
 FROM (
     SELECT user_id, sum(value_2) AS counter FROM events_table GROUP BY user_id
       UNION
-    SELECT user_id, sum(value_2) AS counter FROM users_table GROUP BY user_id OFFSET 4
+    SELECT user_id, sum(value_2) AS counter FROM users_table GROUP BY user_id ORDER BY user_id OFFSET 4
 ) user_id 
-GROUP BY user_id;
+GROUP BY user_id
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ORDER BY 1,2;
-HINT:  Consider using an equality filter on the distributed table's partition column.
+ user_id | sum 
+---------+-----
+       3 | 101
+       4 |  91
+       5 |  94
+       6 |  43
+(4 rows)
+
 -- lower level union does not return partition key with the other relations
 SELECT *
 FROM (
@@ -986,9 +1050,30 @@ FROM (
             GROUP BY 
               user_id) user_id_2
          GROUP BY 
-            user_id)) AS ftop;
+            user_id)) AS ftop
-ERROR:  cannot pushdown the subquery since not all subqueries in the UNION have the partition column in the same position
+ORDER BY 1,2;
-DETAIL:  Each leaf query of the UNION should return the partition column in the same position and all joins must be on the partition column
+ user_id | sum 
+---------+-----
+       1 |  20
+       1 |  62
+       2 |  50
+       2 | 107
+       3 |  55
+       3 | 101
+       4 |  50
+       4 |  91
+       5 |  63
+       5 |  94
+       6 |  21
+       6 |  43
+      22 |   6
+      31 |   5
+      41 |   4
+      42 |   1
+      46 |   3
+      57 |   2
+(18 rows)
+
 -- some UNION all queries that are going to be pulled up
 SELECT 
   count(*)
@@ -998,8 +1083,11 @@ FROM
     UNION ALL
   (SELECT 2 * user_id FROM events_table)
 ) b;
-ERROR:  cannot pushdown the subquery since not all subqueries in the UNION have the partition column in the same position
+ count 
-DETAIL:  Each leaf query of the UNION should return the partition column in the same position and all joins must be on the partition column
+-------
+   202
+(1 row)
+
 -- last query does not have partition key
 SELECT 
   user_id, value_3
@@ -1019,9 +1107,16 @@ FROM
 ) b
 ORDER BY 1 DESC, 2 DESC
 LIMIT 5;
-ERROR:  cannot pushdown the subquery since not all subqueries in the UNION have the partition column in the same position
+ user_id | value_3 
-DETAIL:  Each leaf query of the UNION should return the partition column in the same position and all joins must be on the partition column
+---------+---------
--- we don't allow joins within unions
+       6 |       5
+       6 |       5
+       6 |       3
+       6 |       3
+       6 |       3
+(5 rows)
+
+-- we allow joins within unions
 SELECT 
   count(*)
 FROM 
@@ -1030,11 +1125,12 @@ FROM
     UNION ALL
   (SELECT users_table.user_id FROM events_table, users_table WHERE events_table.user_id = users_table.user_id)
 ) b;
-ERROR:  cannot pushdown the subquery since not all subqueries in the UNION have the partition column in the same position
+ count 
-DETAIL:  Each leaf query of the UNION should return the partition column in the same position and all joins must be on the partition column
+-------
--- we don't support pushing down subqueries without relations
+  1850
--- recursive planning can replace that query, though the whole
+(1 row)
--- query is not safe to pushdown
+
+-- we support unions on subqueries without relations through recursive planning
 SELECT 
   count(*)
 FROM 
@@ -1043,22 +1139,26 @@ FROM
     UNION ALL
   (SELECT 1)
 ) b;
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ count 
-HINT:  Consider using an equality filter on the distributed table's partition column.
+-------
--- we don't support pushing down subqueries without relations
+   102
--- recursive planning can replace that query, though the whole
+(1 row)
--- query is not safe to pushdown
+
+-- we support pushing down subqueries without relations through recursive planning
 SELECT 
-  *
+  count(*)
 FROM 
 (
   (SELECT user_id FROM users_table)
     UNION ALL
   (SELECT (random() * 100)::int)
 ) b;
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ count 
-HINT:  Consider using an equality filter on the distributed table's partition column.
+-------
--- we don't support subqueries without relations
+   102
+(1 row)
+
+-- we support subqueries without relations within a union
 SELECT 
   user_id, value_3
 FROM 
@@ -1077,11 +1177,16 @@ FROM
 ) b
 ORDER BY 1 DESC, 2 DESC
 LIMIT 5;
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ user_id | value_3 
-HINT:  Consider using an equality filter on the distributed table's partition column.
+---------+---------
--- we don't support pushing down subqueries without relations
+       6 |       5
--- recursive planning can replace that query, though the whole
+       6 |       5
--- query is not safe to pushdown
+       6 |       3
+       6 |       3
+       6 |       3
+(5 rows)
+
+-- we support pushing down subqueries without relations through recursive planning
 SELECT ("final_query"."event_types") as types, count(*) AS sumOfEventType
 FROM
   ( SELECT *, random()
@@ -1124,8 +1229,13 @@ FROM
 ) as final_query
 GROUP BY types
 ORDER BY types;
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ types | sumofeventtype 
-HINT:  Consider using an equality filter on the distributed table's partition column.
+-------+----------------
-SET citus.enable_router_execution TO true;
+     0 |             43
+     1 |             42
+     2 |             28
+     3 |              1
+(4 rows)
+
 DROP TABLE events_reference_table;
 DROP TABLE users_reference_table;

src/test/regress/expected/multi_view.out

@@ -543,12 +543,21 @@ SELECT count(*) FROM events_table et WHERE et.user_id IN (SELECT user_id FROM re
     15
 (1 row)
 
--- expected this to work but it did not
+-- union between views is supported through recursive planning
 (SELECT user_id FROM recent_users) 
 UNION
-(SELECT user_id FROM selected_users);
+(SELECT user_id FROM selected_users)
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ORDER BY 1;
-HINT:  Consider using an equality filter on the distributed table's partition column.
+ user_id 
+---------
+       1
+       2
+       3
+       4
+       5
+       6
+(6 rows)
+
 -- wrapping it inside a SELECT * works
 SELECT *
 	FROM (
@@ -587,15 +596,18 @@ SELECT count(*)
      1
 (1 row)
 
--- expected this to work but it does not
+-- UNION ALL between views is supported through recursive planning
 SELECT count(*)
 	FROM (
 		(SELECT user_id FROM recent_users) 
 		UNION ALL
 		(SELECT user_id FROM selected_users) ) u
 	WHERE user_id < 2 AND user_id > 0;
-ERROR:  cannot pushdown the subquery since not all subqueries in the UNION have the partition column in the same position
+ count 
-DETAIL:  Each leaf query of the UNION should return the partition column in the same position and all joins must be on the partition column
+-------
+     2
+(1 row)
+
 -- expand view definitions and re-run last 2 queries
 SELECT count(*)
 	FROM (
@@ -620,8 +632,11 @@ SELECT count(*)
 		UNION ALL
 		(SELECT user_id FROM (SELECT * FROM users_table WHERE value_1 >= 1 and value_1 < 3) bb) ) u
 	WHERE user_id < 2 AND user_id > 0;
-ERROR:  cannot pushdown the subquery since not all subqueries in the UNION have the partition column in the same position
+ count 
-DETAIL:  Each leaf query of the UNION should return the partition column in the same position and all joins must be on the partition column
+-------
+     2
+(1 row)
+
 -- test distinct
 -- distinct is supported if it is on a partition key
 CREATE VIEW distinct_user_with_value_1_3 AS SELECT DISTINCT user_id FROM users_table WHERE value_1 = 3;
@@ -830,7 +845,7 @@ EXPLAIN (COSTS FALSE) SELECT et.* FROM recent_10_users JOIN events_table et USIN
    ->  Sort
          Sort Key: remote_scan."time" DESC
          ->  Custom Scan (Citus Real-Time)
-               ->  Distributed Subplan 83_1
+               ->  Distributed Subplan 91_1
                      ->  Limit
                            ->  Sort
                                  Sort Key: max((max(remote_scan.lastseen))) DESC

src/test/regress/expected/set_operation_and_local_tables.out

@@ -0,0 +1,321 @@
+CREATE SCHEMA recursive_set_local;
+SET search_path TO recursive_set_local, public;
+CREATE TABLE recursive_set_local.test (x int, y int);
+SELECT create_distributed_table('test', 'x');
+ create_distributed_table 
+--------------------------
+ 
+(1 row)
+
+CREATE TABLE recursive_set_local.ref (a int, b int);
+SELECT create_reference_table('ref');
+ create_reference_table 
+------------------------
+ 
+(1 row)
+
+CREATE TABLE recursive_set_local.local_test (x int, y int);
+INSERT INTO test VALUES (1,1), (2,2);
+INSERT INTO ref VALUES (2,2), (3,3);
+INSERT INTO local_test VALUES (3,3), (4,4);
+SET client_min_messages TO DEBUG;
+-- we should be able to run set operations with local tables
+(SELECT x FROM test) INTERSECT (SELECT x FROM local_test) ORDER BY 1 DESC;
+DEBUG:  generating subplan 3_1 for subquery SELECT x FROM recursive_set_local.local_test
+DEBUG:  generating subplan 3_2 for subquery SELECT x FROM recursive_set_local.test
+DEBUG:  Plan 3 query after replacing subqueries and CTEs: SELECT intermediate_result.x FROM read_intermediate_result('3_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer) INTERSECT SELECT intermediate_result.x FROM read_intermediate_result('3_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer) ORDER BY 1 DESC
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x 
+---
+(0 rows)
+
+-- we should be able to run set operations with generate series
+(SELECT x FROM test) INTERSECT (SELECT i FROM generate_series(0, 100) i) ORDER BY 1 DESC;
+DEBUG:  generating subplan 5_1 for subquery SELECT x FROM recursive_set_local.test
+DEBUG:  Plan 5 query after replacing subqueries and CTEs: SELECT intermediate_result.x FROM read_intermediate_result('5_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer) INTERSECT SELECT i.i FROM generate_series(0, 100) i(i) ORDER BY 1 DESC
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x 
+---
+ 2
+ 1
+(2 rows)
+
+-- we'd first recursively plan the query with "test", thus don't need to recursively 
+-- plan other query
+(SELECT x FROM test LIMIT 5) INTERSECT (SELECT i FROM generate_series(0, 100) i) ORDER BY 1 DESC;
+DEBUG:  push down of limit count: 5
+DEBUG:  generating subplan 7_1 for subquery SELECT x FROM recursive_set_local.test LIMIT 5
+DEBUG:  Plan 7 query after replacing subqueries and CTEs: SELECT intermediate_result.x FROM read_intermediate_result('7_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer) INTERSECT SELECT i.i FROM generate_series(0, 100) i(i) ORDER BY 1 DESC
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x 
+---
+ 2
+ 1
+(2 rows)
+
+-- this doesn't require any recursive planning
+(SELECT a FROM ref) INTERSECT (SELECT i FROM generate_series(0, 100) i) ORDER BY 1 DESC;
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ a 
+---
+ 3
+ 2
+(2 rows)
+
+-- same query with a failure on the worker (i.e., division by zero)
+(SELECT x FROM test) INTERSECT (SELECT i/0 FROM generate_series(0, 100) i) ORDER BY 1 DESC;
+DEBUG:  generating subplan 10_1 for subquery SELECT x FROM recursive_set_local.test
+DEBUG:  Plan 10 query after replacing subqueries and CTEs: SELECT intermediate_result.x FROM read_intermediate_result('10_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer) INTERSECT SELECT (i.i / 0) FROM generate_series(0, 100) i(i) ORDER BY 1 DESC
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+WARNING:  division by zero
+CONTEXT:  while executing command on localhost:57637
+ERROR:  could not receive query results
+-- we should be able to run set operations with generate series and local tables as well
+((SELECT x FROM local_test) UNION ALL (SELECT x FROM test)) INTERSECT (SELECT i FROM generate_series(0, 100) i) ORDER BY 1 DESC;
+DEBUG:  generating subplan 12_1 for subquery SELECT x FROM recursive_set_local.local_test
+DEBUG:  generating subplan 12_2 for subquery SELECT x FROM recursive_set_local.test
+DEBUG:  Plan 12 query after replacing subqueries and CTEs: (SELECT intermediate_result.x FROM read_intermediate_result('12_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer) UNION ALL SELECT intermediate_result.x FROM read_intermediate_result('12_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer)) INTERSECT SELECT i.i FROM generate_series(0, 100) i(i) ORDER BY 1 DESC
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x 
+---
+ 4
+ 3
+ 2
+ 1
+(4 rows)
+
+-- two local tables are on different leaf queries, so safe to plan & execute
+((SELECT x FROM local_test) UNION ALL (SELECT x FROM test)) INTERSECT (SELECT x FROM local_test) ORDER BY 1 DESC;
+DEBUG:  generating subplan 14_1 for subquery SELECT x FROM recursive_set_local.local_test
+DEBUG:  generating subplan 14_2 for subquery SELECT x FROM recursive_set_local.local_test
+DEBUG:  generating subplan 14_3 for subquery SELECT x FROM recursive_set_local.test
+DEBUG:  Plan 14 query after replacing subqueries and CTEs: (SELECT intermediate_result.x FROM read_intermediate_result('14_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer) UNION ALL SELECT intermediate_result.x FROM read_intermediate_result('14_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer)) INTERSECT SELECT intermediate_result.x FROM read_intermediate_result('14_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer) ORDER BY 1 DESC
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x 
+---
+ 4
+ 3
+(2 rows)
+
+-- use ctes inside unions along with local tables on the top level
+WITH 
+cte_1 AS (SELECT user_id FROM users_table),
+cte_2 AS (SELECT user_id FROM events_table)
+((SELECT * FROM cte_1) UNION (SELECT * FROM cte_2) UNION (SELECT x FROM local_test)) INTERSECT (SELECT i FROM generate_series(0, 100) i)
+ORDER BY 1 DESC;
+DEBUG:  generating subplan 16_1 for CTE cte_1: SELECT user_id FROM public.users_table
+DEBUG:  generating subplan 16_2 for CTE cte_2: SELECT user_id FROM public.events_table
+DEBUG:  generating subplan 16_3 for subquery SELECT x FROM recursive_set_local.local_test
+DEBUG:  Plan 16 query after replacing subqueries and CTEs: (SELECT cte_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('16_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_1 UNION SELECT cte_2.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('16_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_2 UNION SELECT intermediate_result.x FROM read_intermediate_result('16_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer)) INTERSECT SELECT i.i FROM generate_series(0, 100) i(i) ORDER BY 1 DESC
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ user_id 
+---------
+       6
+       5
+       4
+       3
+       2
+       1
+(6 rows)
+
+-- CTEs inside subqueries unioned with local table
+-- final query is real-time
+SELECT
+	count(*)
+FROM
+	(
+		((WITH cte_1 AS (SELECT x FROM test) SELECT * FROM cte_1) UNION 
+		(WITH cte_1 AS (SELECT a FROM ref) SELECT * FROM cte_1)) INTERSECT
+		(SELECT x FROM local_test)
+	) as foo,
+	test
+	WHERE test.y = foo.x;
+DEBUG:  generating subplan 19_1 for CTE cte_1: SELECT x FROM recursive_set_local.test
+DEBUG:  generating subplan 19_2 for CTE cte_1: SELECT a FROM recursive_set_local.ref
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 19_3 for subquery SELECT x FROM recursive_set_local.local_test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 19_4 for subquery (SELECT cte_1.x FROM (SELECT intermediate_result.x FROM read_intermediate_result('19_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer)) cte_1 UNION SELECT cte_1.a FROM (SELECT intermediate_result.a FROM read_intermediate_result('19_2'::text, 'binary'::citus_copy_format) intermediate_result(a integer)) cte_1) INTERSECT SELECT intermediate_result.x FROM read_intermediate_result('19_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer)
+DEBUG:  Plan 19 query after replacing subqueries and CTEs: SELECT count(*) AS count FROM (SELECT intermediate_result.x FROM read_intermediate_result('19_4'::text, 'binary'::citus_copy_format) intermediate_result(x integer)) foo, recursive_set_local.test WHERE (test.y = foo.x)
+ count 
+-------
+     0
+(1 row)
+
+-- CTEs inside subqueries unioned with local table
+-- final query is router
+SELECT
+	count(*)
+FROM
+	(
+		((WITH cte_1 AS (SELECT x FROM test) SELECT * FROM cte_1) UNION 
+		(WITH cte_1 AS (SELECT a FROM ref) SELECT * FROM cte_1)) INTERSECT
+		(SELECT x FROM local_test)
+	) as foo,
+	ref
+	WHERE ref.a = foo.x;
+DEBUG:  generating subplan 23_1 for CTE cte_1: SELECT x FROM recursive_set_local.test
+DEBUG:  generating subplan 23_2 for CTE cte_1: SELECT a FROM recursive_set_local.ref
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 23_3 for subquery SELECT x FROM recursive_set_local.local_test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 23_4 for subquery (SELECT cte_1.x FROM (SELECT intermediate_result.x FROM read_intermediate_result('23_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer)) cte_1 UNION SELECT cte_1.a FROM (SELECT intermediate_result.a FROM read_intermediate_result('23_2'::text, 'binary'::citus_copy_format) intermediate_result(a integer)) cte_1) INTERSECT SELECT intermediate_result.x FROM read_intermediate_result('23_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer)
+DEBUG:  Plan 23 query after replacing subqueries and CTEs: SELECT count(*) AS count FROM (SELECT intermediate_result.x FROM read_intermediate_result('23_4'::text, 'binary'::citus_copy_format) intermediate_result(x integer)) foo, recursive_set_local.ref WHERE (ref.a = foo.x)
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ count 
+-------
+     1
+(1 row)
+
+-- subquery union in WHERE clause without parition column equality is recursively planned including the local tables
+SELECT * FROM test a WHERE x IN (SELECT x FROM test b UNION SELECT y FROM test c UNION SELECT y FROM local_test d) ORDER BY 1,2;
+DEBUG:  generating subplan 27_1 for subquery SELECT y FROM recursive_set_local.local_test d
+DEBUG:  generating subplan 27_2 for subquery SELECT x FROM recursive_set_local.test b
+DEBUG:  generating subplan 27_3 for subquery SELECT y FROM recursive_set_local.test c
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 27_4 for subquery SELECT intermediate_result.x FROM read_intermediate_result('27_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer) UNION SELECT intermediate_result.y FROM read_intermediate_result('27_3'::text, 'binary'::citus_copy_format) intermediate_result(y integer) UNION SELECT intermediate_result.y FROM read_intermediate_result('27_1'::text, 'binary'::citus_copy_format) intermediate_result(y integer)
+DEBUG:  Plan 27 query after replacing subqueries and CTEs: SELECT x, y FROM recursive_set_local.test a WHERE (x IN (SELECT intermediate_result.x FROM read_intermediate_result('27_4'::text, 'binary'::citus_copy_format) intermediate_result(x integer))) ORDER BY x, y
+ x | y 
+---+---
+ 1 | 1
+ 2 | 2
+(2 rows)
+
+-- same query with subquery in where is wrapped in CTE
+SELECT * FROM test a WHERE x IN (WITH cte AS (SELECT x FROM test b UNION SELECT y FROM test c UNION SELECT y FROM local_test d) SELECT * FROM cte) ORDER BY 1,2;
+DEBUG:  generating subplan 31_1 for CTE cte: SELECT b.x FROM recursive_set_local.test b UNION SELECT c.y FROM recursive_set_local.test c UNION SELECT d.y FROM recursive_set_local.local_test d
+DEBUG:  generating subplan 32_1 for subquery SELECT y FROM recursive_set_local.local_test d
+DEBUG:  generating subplan 32_2 for subquery SELECT x FROM recursive_set_local.test b
+DEBUG:  generating subplan 32_3 for subquery SELECT y FROM recursive_set_local.test c
+DEBUG:  Plan 32 query after replacing subqueries and CTEs: SELECT intermediate_result.x FROM read_intermediate_result('32_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer) UNION SELECT intermediate_result.y FROM read_intermediate_result('32_3'::text, 'binary'::citus_copy_format) intermediate_result(y integer) UNION SELECT intermediate_result.y FROM read_intermediate_result('32_1'::text, 'binary'::citus_copy_format) intermediate_result(y integer)
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  Plan 31 query after replacing subqueries and CTEs: SELECT x, y FROM recursive_set_local.test a WHERE (x IN (SELECT cte.x FROM (SELECT intermediate_result.x FROM read_intermediate_result('31_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer)) cte)) ORDER BY x, y
+ x | y 
+---+---
+ 1 | 1
+ 2 | 2
+(2 rows)
+
+-- not supported since local table is joined with a set operation
+SELECT * FROM ((SELECT * FROM test) EXCEPT (SELECT * FROM test ORDER BY x LIMIT 1)) u JOIN local_test USING (x) ORDER BY 1,2;
+DEBUG:  push down of limit count: 1
+DEBUG:  generating subplan 35_1 for subquery SELECT x, y FROM recursive_set_local.test ORDER BY x LIMIT 1
+DEBUG:  generating subplan 35_2 for subquery SELECT x, y FROM recursive_set_local.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 35_3 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('35_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) EXCEPT SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('35_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)
+DEBUG:  Plan 35 query after replacing subqueries and CTEs: SELECT u.x, u.y, local_test.y FROM ((SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('35_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u JOIN recursive_set_local.local_test USING (x)) ORDER BY u.x, u.y
+ERROR:  relation local_test is not distributed
+-- though we replace some queries including the local query, the intermediate result is on the outer part of an outer join 
+SELECT * FROM ((SELECT * FROM local_test) INTERSECT (SELECT * FROM test ORDER BY x LIMIT 1)) u LEFT JOIN test USING (x) ORDER BY 1,2;
+DEBUG:  generating subplan 39_1 for subquery SELECT x, y FROM recursive_set_local.local_test
+DEBUG:  push down of limit count: 1
+DEBUG:  generating subplan 39_2 for subquery SELECT x, y FROM recursive_set_local.test ORDER BY x LIMIT 1
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 39_3 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('39_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) INTERSECT SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('39_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)
+DEBUG:  Plan 39 query after replacing subqueries and CTEs: SELECT u.x, u.y, test.y FROM ((SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('39_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u LEFT JOIN recursive_set_local.test USING (x)) ORDER BY u.x, u.y
+ERROR:  cannot pushdown the subquery
+DETAIL:  Complex subqueries and CTEs cannot be in the outer part of the outer join
+-- we replace some queries including the local query, the intermediate result is on the inner part of an outer join 
+SELECT * FROM ((SELECT * FROM local_test) INTERSECT (SELECT * FROM test ORDER BY x LIMIT 1)) u RIGHT JOIN test USING (x) ORDER BY 1,2;
+DEBUG:  generating subplan 42_1 for subquery SELECT x, y FROM recursive_set_local.local_test
+DEBUG:  push down of limit count: 1
+DEBUG:  generating subplan 42_2 for subquery SELECT x, y FROM recursive_set_local.test ORDER BY x LIMIT 1
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 42_3 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('42_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) INTERSECT SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('42_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)
+DEBUG:  Plan 42 query after replacing subqueries and CTEs: SELECT test.x, u.y, test.y FROM ((SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('42_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u RIGHT JOIN recursive_set_local.test USING (x)) ORDER BY test.x, u.y
+ x | y | y 
+---+---+---
+ 1 |   | 1
+ 2 |   | 2
+(2 rows)
+
+-- recurively plan left part of the join, and run a final real-time query
+SELECT * FROM ((SELECT * FROM local_test) INTERSECT (SELECT * FROM test ORDER BY x LIMIT 1)) u INNER JOIN test USING (x) ORDER BY 1,2;
+DEBUG:  generating subplan 45_1 for subquery SELECT x, y FROM recursive_set_local.local_test
+DEBUG:  push down of limit count: 1
+DEBUG:  generating subplan 45_2 for subquery SELECT x, y FROM recursive_set_local.test ORDER BY x LIMIT 1
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 45_3 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('45_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) INTERSECT SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('45_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)
+DEBUG:  Plan 45 query after replacing subqueries and CTEs: SELECT u.x, u.y, test.y FROM ((SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('45_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u JOIN recursive_set_local.test USING (x)) ORDER BY u.x, u.y
+ x | y | y 
+---+---+---
+(0 rows)
+
+-- distributed table in WHERE clause, but not FROM clause still disallowed
+SELECT * FROM ((SELECT x FROM test) UNION (SELECT x FROM (SELECT x FROM local_test) as foo WHERE x IN (SELECT x FROM test))) u ORDER BY 1;
+DEBUG:  generating subplan 48_1 for subquery SELECT x FROM recursive_set_local.local_test
+ERROR:  cannot pushdown the subquery
+DETAIL:  Complex subqueries and CTEs are not allowed in the FROM clause when the query has subqueries in the WHERE clause
+SET citus.enable_repartition_joins TO ON;
+--  repartition is recursively planned before the set operation
+(SELECT x FROM test) INTERSECT (SELECT t1.x FROM test as t1, test as t2 WHERE t1.x = t2.y LIMIT 2) INTERSECT (((SELECT x FROM local_test) UNION ALL (SELECT x FROM test)) INTERSECT (SELECT i FROM generate_series(0, 100) i)) ORDER BY 1 DESC; 
+DEBUG:  push down of limit count: 2
+DEBUG:  join prunable for task partitionId 0 and 1
+DEBUG:  join prunable for task partitionId 0 and 2
+DEBUG:  join prunable for task partitionId 0 and 3
+DEBUG:  join prunable for task partitionId 1 and 0
+DEBUG:  join prunable for task partitionId 1 and 2
+DEBUG:  join prunable for task partitionId 1 and 3
+DEBUG:  join prunable for task partitionId 2 and 0
+DEBUG:  join prunable for task partitionId 2 and 1
+DEBUG:  join prunable for task partitionId 2 and 3
+DEBUG:  join prunable for task partitionId 3 and 0
+DEBUG:  join prunable for task partitionId 3 and 1
+DEBUG:  join prunable for task partitionId 3 and 2
+DEBUG:  pruning merge fetch taskId 1
+DETAIL:  Creating dependency on merge taskId 9
+DEBUG:  pruning merge fetch taskId 2
+DETAIL:  Creating dependency on merge taskId 9
+DEBUG:  pruning merge fetch taskId 4
+DETAIL:  Creating dependency on merge taskId 14
+DEBUG:  pruning merge fetch taskId 5
+DETAIL:  Creating dependency on merge taskId 14
+DEBUG:  pruning merge fetch taskId 7
+DETAIL:  Creating dependency on merge taskId 19
+DEBUG:  pruning merge fetch taskId 8
+DETAIL:  Creating dependency on merge taskId 19
+DEBUG:  pruning merge fetch taskId 10
+DETAIL:  Creating dependency on merge taskId 24
+DEBUG:  pruning merge fetch taskId 11
+DETAIL:  Creating dependency on merge taskId 24
+DEBUG:  cannot use real time executor with repartition jobs
+HINT:  Since you enabled citus.enable_repartition_joins Citus chose to use task-tracker.
+DEBUG:  generating subplan 50_1 for subquery SELECT t1.x FROM recursive_set_local.test t1, recursive_set_local.test t2 WHERE (t1.x = t2.y) LIMIT 2
+DEBUG:  generating subplan 50_2 for subquery SELECT x FROM recursive_set_local.local_test
+DEBUG:  generating subplan 50_3 for subquery SELECT x FROM recursive_set_local.test
+DEBUG:  generating subplan 50_4 for subquery SELECT x FROM recursive_set_local.test
+DEBUG:  Plan 50 query after replacing subqueries and CTEs: SELECT intermediate_result.x FROM read_intermediate_result('50_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer) INTERSECT SELECT intermediate_result.x FROM read_intermediate_result('50_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer) INTERSECT ((SELECT intermediate_result.x FROM read_intermediate_result('50_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer) UNION ALL SELECT intermediate_result.x FROM read_intermediate_result('50_4'::text, 'binary'::citus_copy_format) intermediate_result(x integer)) INTERSECT SELECT i.i FROM generate_series(0, 100) i(i)) ORDER BY 1 DESC
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x 
+---
+ 2
+ 1
+(2 rows)
+
+SET citus.enable_repartition_joins TO OFF;
+RESET client_min_messages;
+DROP SCHEMA recursive_set_local CASCADE;
+NOTICE:  drop cascades to 3 other objects
+DETAIL:  drop cascades to table test
+drop cascades to table ref
+drop cascades to table local_test

src/test/regress/expected/set_operations.out

@@ -0,0 +1,868 @@
+CREATE SCHEMA recursive_union;
+SET search_path TO recursive_union, public;
+CREATE TABLE recursive_union.test (x int, y int);
+SELECT create_distributed_table('test', 'x');
+ create_distributed_table 
+--------------------------
+ 
+(1 row)
+
+CREATE TABLE recursive_union.ref (a int, b int);
+SELECT create_reference_table('ref');
+ create_reference_table 
+------------------------
+ 
+(1 row)
+
+INSERT INTO test VALUES (1,1), (2,2);
+INSERT INTO ref VALUES (2,2), (3,3);
+-- top-level set operations are supported through recursive planning
+SET client_min_messages TO DEBUG;
+(SELECT * FROM test) UNION (SELECT * FROM test) ORDER BY 1,2;
+DEBUG:  generating subplan 3_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  generating subplan 3_2 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Plan 3 query after replacing subqueries and CTEs: SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('3_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) UNION SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('3_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) ORDER BY 1, 2
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+ 1 | 1
+ 2 | 2
+(2 rows)
+
+(SELECT * FROM test) UNION (SELECT * FROM ref) ORDER BY 1,2;
+DEBUG:  generating subplan 6_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Plan 6 query after replacing subqueries and CTEs: SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('6_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) UNION SELECT ref.a, ref.b FROM recursive_union.ref ORDER BY 1, 2
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+ 1 | 1
+ 2 | 2
+ 3 | 3
+(3 rows)
+
+(SELECT * FROM ref) UNION (SELECT * FROM ref) ORDER BY 1,2;
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ a | b 
+---+---
+ 2 | 2
+ 3 | 3
+(2 rows)
+
+(SELECT * FROM test) UNION ALL (SELECT * FROM test) ORDER BY 1,2;
+DEBUG:  generating subplan 9_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  generating subplan 9_2 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Plan 9 query after replacing subqueries and CTEs: SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('9_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) UNION ALL SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('9_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) ORDER BY 1, 2
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+ 1 | 1
+ 1 | 1
+ 2 | 2
+ 2 | 2
+(4 rows)
+
+(SELECT * FROM test) UNION ALL (SELECT * FROM ref) ORDER BY 1,2;
+DEBUG:  generating subplan 12_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Plan 12 query after replacing subqueries and CTEs: SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('12_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) UNION ALL SELECT ref.a, ref.b FROM recursive_union.ref ORDER BY 1, 2
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+ 1 | 1
+ 2 | 2
+ 2 | 2
+ 3 | 3
+(4 rows)
+
+(SELECT * FROM ref) UNION ALL (SELECT * FROM ref) ORDER BY 1,2;
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ a | b 
+---+---
+ 2 | 2
+ 2 | 2
+ 3 | 3
+ 3 | 3
+(4 rows)
+
+(SELECT * FROM test) INTERSECT (SELECT * FROM test) ORDER BY 1,2;
+DEBUG:  generating subplan 15_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  generating subplan 15_2 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Plan 15 query after replacing subqueries and CTEs: SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('15_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) INTERSECT SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('15_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) ORDER BY 1, 2
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+ 1 | 1
+ 2 | 2
+(2 rows)
+
+(SELECT * FROM test) INTERSECT (SELECT * FROM ref) ORDER BY 1,2;
+DEBUG:  generating subplan 18_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Plan 18 query after replacing subqueries and CTEs: SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('18_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) INTERSECT SELECT ref.a, ref.b FROM recursive_union.ref ORDER BY 1, 2
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+ 2 | 2
+(1 row)
+
+(SELECT * FROM ref) INTERSECT (SELECT * FROM ref) ORDER BY 1,2;
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ a | b 
+---+---
+ 2 | 2
+ 3 | 3
+(2 rows)
+
+(SELECT * FROM test) INTERSECT ALL (SELECT * FROM test) ORDER BY 1,2;
+DEBUG:  generating subplan 21_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  generating subplan 21_2 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Plan 21 query after replacing subqueries and CTEs: SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('21_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) INTERSECT ALL SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('21_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) ORDER BY 1, 2
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+ 1 | 1
+ 2 | 2
+(2 rows)
+
+(SELECT * FROM test) INTERSECT ALL (SELECT * FROM ref) ORDER BY 1,2;
+DEBUG:  generating subplan 24_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Plan 24 query after replacing subqueries and CTEs: SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('24_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) INTERSECT ALL SELECT ref.a, ref.b FROM recursive_union.ref ORDER BY 1, 2
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+ 2 | 2
+(1 row)
+
+(SELECT * FROM ref) INTERSECT ALL (SELECT * FROM ref) ORDER BY 1,2;
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ a | b 
+---+---
+ 2 | 2
+ 3 | 3
+(2 rows)
+
+(SELECT * FROM test) EXCEPT (SELECT * FROM test) ORDER BY 1,2;
+DEBUG:  generating subplan 27_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  generating subplan 27_2 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Plan 27 query after replacing subqueries and CTEs: SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('27_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) EXCEPT SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('27_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) ORDER BY 1, 2
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+(0 rows)
+
+(SELECT * FROM test) EXCEPT (SELECT * FROM ref) ORDER BY 1,2;
+DEBUG:  generating subplan 30_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Plan 30 query after replacing subqueries and CTEs: SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('30_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) EXCEPT SELECT ref.a, ref.b FROM recursive_union.ref ORDER BY 1, 2
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+ 1 | 1
+(1 row)
+
+(SELECT * FROM ref) EXCEPT (SELECT * FROM ref) ORDER BY 1,2;
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ a | b 
+---+---
+(0 rows)
+
+(SELECT * FROM test) EXCEPT ALL (SELECT * FROM test) ORDER BY 1,2;
+DEBUG:  generating subplan 33_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  generating subplan 33_2 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Plan 33 query after replacing subqueries and CTEs: SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('33_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) EXCEPT ALL SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('33_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) ORDER BY 1, 2
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+(0 rows)
+
+(SELECT * FROM test) EXCEPT ALL (SELECT * FROM ref) ORDER BY 1,2;
+DEBUG:  generating subplan 36_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Plan 36 query after replacing subqueries and CTEs: SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('36_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) EXCEPT ALL SELECT ref.a, ref.b FROM recursive_union.ref ORDER BY 1, 2
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+ 1 | 1
+(1 row)
+
+(SELECT * FROM ref) EXCEPT ALL (SELECT * FROM ref) ORDER BY 1,2;
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ a | b 
+---+---
+(0 rows)
+
+-- more complex set operation trees are supported
+(SELECT * FROM test)
+INTERSECT
+(SELECT * FROM ref)
+UNION ALL
+(SELECT s, s FROM generate_series(1,10) s)
+EXCEPT
+(SELECT 1,1)
+UNION
+(SELECT test.x, ref.a FROM test LEFT JOIN ref ON (x = a))
+ORDER BY 1,2;
+DEBUG:  generating subplan 39_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  generating subplan 39_2 for subquery SELECT test.x, ref.a FROM (recursive_union.test LEFT JOIN recursive_union.ref ON ((test.x = ref.a)))
+DEBUG:  Plan 39 query after replacing subqueries and CTEs: (((SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('39_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) INTERSECT SELECT ref.a, ref.b FROM recursive_union.ref) UNION ALL SELECT s.s, s.s FROM generate_series(1, 10) s(s)) EXCEPT SELECT 1, 1) UNION SELECT intermediate_result.x, intermediate_result.a FROM read_intermediate_result('39_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, a integer) ORDER BY 1, 2
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x  | y  
+----+----
+  1 |   
+  2 |  2
+  3 |  3
+  4 |  4
+  5 |  5
+  6 |  6
+  7 |  7
+  8 |  8
+  9 |  9
+ 10 | 10
+(10 rows)
+
+-- within a subquery, some unions can be pushed down
+SELECT * FROM ((SELECT * FROM test) UNION (SELECT * FROM test)) u ORDER BY 1,2;
+ x | y 
+---+---
+ 1 | 1
+ 2 | 2
+(2 rows)
+
+SELECT * FROM ((SELECT x, y FROM test) UNION (SELECT y, x FROM test)) u ORDER BY 1,2;
+DEBUG:  generating subplan 43_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  generating subplan 43_2 for subquery SELECT y, x FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 43_3 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('43_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) UNION SELECT intermediate_result.y, intermediate_result.x FROM read_intermediate_result('43_2'::text, 'binary'::citus_copy_format) intermediate_result(y integer, x integer)
+DEBUG:  Plan 43 query after replacing subqueries and CTEs: SELECT x, y FROM (SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('43_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u ORDER BY x, y
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+ 1 | 1
+ 2 | 2
+(2 rows)
+
+SELECT * FROM ((SELECT * FROM test) UNION (SELECT * FROM ref)) u ORDER BY 1,2;
+DEBUG:  generating subplan 47_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 47_2 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('47_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) UNION SELECT ref.a, ref.b FROM recursive_union.ref
+DEBUG:  Plan 47 query after replacing subqueries and CTEs: SELECT x, y FROM (SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('47_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u ORDER BY x, y
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+ 1 | 1
+ 2 | 2
+ 3 | 3
+(3 rows)
+
+SELECT * FROM ((SELECT * FROM ref) UNION (SELECT * FROM ref)) u ORDER BY 1,2;
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ a | b 
+---+---
+ 2 | 2
+ 3 | 3
+(2 rows)
+
+SELECT * FROM ((SELECT * FROM test) UNION ALL (SELECT * FROM test)) u ORDER BY 1,2;
+ x | y 
+---+---
+ 1 | 1
+ 1 | 1
+ 2 | 2
+ 2 | 2
+(4 rows)
+
+SELECT * FROM ((SELECT x, y FROM test) UNION ALL (SELECT y, x FROM test)) u ORDER BY 1,2;
+ x | y 
+---+---
+ 1 | 1
+ 1 | 1
+ 2 | 2
+ 2 | 2
+(4 rows)
+
+SELECT * FROM ((SELECT * FROM test) UNION ALL (SELECT * FROM ref)) u ORDER BY 1,2;
+DEBUG:  generating subplan 53_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 53_2 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('53_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) UNION ALL SELECT ref.a, ref.b FROM recursive_union.ref
+DEBUG:  Plan 53 query after replacing subqueries and CTEs: SELECT x, y FROM (SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('53_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u ORDER BY x, y
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+ 1 | 1
+ 2 | 2
+ 2 | 2
+ 3 | 3
+(4 rows)
+
+SELECT * FROM ((SELECT * FROM ref) UNION ALL (SELECT * FROM ref)) u ORDER BY 1,2;
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ a | b 
+---+---
+ 2 | 2
+ 2 | 2
+ 3 | 3
+ 3 | 3
+(4 rows)
+
+SELECT * FROM ((SELECT * FROM test) INTERSECT (SELECT * FROM test)) u ORDER BY 1,2;
+DEBUG:  generating subplan 57_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  generating subplan 57_2 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 57_3 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('57_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) INTERSECT SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('57_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)
+DEBUG:  Plan 57 query after replacing subqueries and CTEs: SELECT x, y FROM (SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('57_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u ORDER BY x, y
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+ 1 | 1
+ 2 | 2
+(2 rows)
+
+SELECT * FROM ((SELECT x, y FROM test) INTERSECT (SELECT y, x FROM test)) u ORDER BY 1,2;
+DEBUG:  generating subplan 61_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  generating subplan 61_2 for subquery SELECT y, x FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 61_3 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('61_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) INTERSECT SELECT intermediate_result.y, intermediate_result.x FROM read_intermediate_result('61_2'::text, 'binary'::citus_copy_format) intermediate_result(y integer, x integer)
+DEBUG:  Plan 61 query after replacing subqueries and CTEs: SELECT x, y FROM (SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('61_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u ORDER BY x, y
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+ 1 | 1
+ 2 | 2
+(2 rows)
+
+SELECT * FROM ((SELECT * FROM test) INTERSECT (SELECT * FROM ref)) u ORDER BY 1,2;
+DEBUG:  generating subplan 65_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 65_2 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('65_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) INTERSECT SELECT ref.a, ref.b FROM recursive_union.ref
+DEBUG:  Plan 65 query after replacing subqueries and CTEs: SELECT x, y FROM (SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('65_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u ORDER BY x, y
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+ 2 | 2
+(1 row)
+
+SELECT * FROM ((SELECT * FROM ref) INTERSECT (SELECT * FROM ref)) u ORDER BY 1,2;
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ a | b 
+---+---
+ 2 | 2
+ 3 | 3
+(2 rows)
+
+SELECT * FROM ((SELECT * FROM test) EXCEPT (SELECT * FROM test)) u ORDER BY 1,2;
+DEBUG:  generating subplan 69_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  generating subplan 69_2 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 69_3 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('69_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) EXCEPT SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('69_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)
+DEBUG:  Plan 69 query after replacing subqueries and CTEs: SELECT x, y FROM (SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('69_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u ORDER BY x, y
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+(0 rows)
+
+SELECT * FROM ((SELECT x, y FROM test) EXCEPT (SELECT y, x FROM test)) u ORDER BY 1,2;
+DEBUG:  generating subplan 73_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  generating subplan 73_2 for subquery SELECT y, x FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 73_3 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('73_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) EXCEPT SELECT intermediate_result.y, intermediate_result.x FROM read_intermediate_result('73_2'::text, 'binary'::citus_copy_format) intermediate_result(y integer, x integer)
+DEBUG:  Plan 73 query after replacing subqueries and CTEs: SELECT x, y FROM (SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('73_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u ORDER BY x, y
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+(0 rows)
+
+SELECT * FROM ((SELECT * FROM test) EXCEPT (SELECT * FROM ref)) u ORDER BY 1,2;
+DEBUG:  generating subplan 77_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 77_2 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('77_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) EXCEPT SELECT ref.a, ref.b FROM recursive_union.ref
+DEBUG:  Plan 77 query after replacing subqueries and CTEs: SELECT x, y FROM (SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('77_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u ORDER BY x, y
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+ 1 | 1
+(1 row)
+
+SELECT * FROM ((SELECT * FROM ref) EXCEPT (SELECT * FROM ref)) u ORDER BY 1,2;
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ a | b 
+---+---
+(0 rows)
+
+-- unions can even be pushed down within a join
+SELECT * FROM ((SELECT * FROM test) UNION (SELECT * FROM test)) u JOIN test USING (x) ORDER BY 1,2;
+ x | y | y 
+---+---+---
+ 1 | 1 | 1
+ 2 | 2 | 2
+(2 rows)
+
+SELECT * FROM ((SELECT * FROM test) UNION ALL (SELECT * FROM test)) u LEFT JOIN test USING (x) ORDER BY 1,2;
+ x | y | y 
+---+---+---
+ 1 | 1 | 1
+ 1 | 1 | 1
+ 2 | 2 | 2
+ 2 | 2 | 2
+(4 rows)
+
+-- unions cannot be pushed down if one leaf recurs
+SELECT * FROM ((SELECT * FROM test) UNION (SELECT * FROM test ORDER BY x LIMIT 1)) u JOIN test USING (x) ORDER BY 1,2;
+DEBUG:  push down of limit count: 1
+DEBUG:  generating subplan 83_1 for subquery SELECT x, y FROM recursive_union.test ORDER BY x LIMIT 1
+DEBUG:  generating subplan 83_2 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 83_3 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('83_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) UNION SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('83_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)
+DEBUG:  Plan 83 query after replacing subqueries and CTEs: SELECT u.x, u.y, test.y FROM ((SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('83_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u JOIN recursive_union.test USING (x)) ORDER BY u.x, u.y
+ x | y | y 
+---+---+---
+ 1 | 1 | 1
+ 2 | 2 | 2
+(2 rows)
+
+SELECT * FROM ((SELECT * FROM test) UNION ALL (SELECT * FROM test ORDER BY x LIMIT 1)) u LEFT JOIN test USING (x) ORDER BY 1,2;
+DEBUG:  push down of limit count: 1
+DEBUG:  generating subplan 87_1 for subquery SELECT x, y FROM recursive_union.test ORDER BY x LIMIT 1
+DEBUG:  generating subplan 87_2 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 87_3 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('87_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) UNION ALL SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('87_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)
+DEBUG:  Plan 87 query after replacing subqueries and CTEs: SELECT u.x, u.y, test.y FROM ((SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('87_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u LEFT JOIN recursive_union.test USING (x)) ORDER BY u.x, u.y
+ERROR:  cannot pushdown the subquery
+DETAIL:  Complex subqueries and CTEs cannot be in the outer part of the outer join
+-- unions in a join without partition column equality (column names from first query are used for join)
+SELECT * FROM ((SELECT x, y FROM test) UNION (SELECT y, x FROM test)) u JOIN test USING (x) ORDER BY 1,2;
+DEBUG:  generating subplan 91_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  generating subplan 91_2 for subquery SELECT y, x FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 91_3 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('91_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) UNION SELECT intermediate_result.y, intermediate_result.x FROM read_intermediate_result('91_2'::text, 'binary'::citus_copy_format) intermediate_result(y integer, x integer)
+DEBUG:  Plan 91 query after replacing subqueries and CTEs: SELECT u.x, u.y, test.y FROM ((SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('91_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u JOIN recursive_union.test USING (x)) ORDER BY u.x, u.y
+ x | y | y 
+---+---+---
+ 1 | 1 | 1
+ 2 | 2 | 2
+(2 rows)
+
+SELECT * FROM ((SELECT x, y FROM test) UNION (SELECT 1, 1 FROM test)) u JOIN test USING (x) ORDER BY 1,2;
+DEBUG:  generating subplan 95_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  generating subplan 95_2 for subquery SELECT 1, 1 FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 95_3 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('95_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) UNION SELECT intermediate_result."?column?", intermediate_result."?column?_1" AS "?column?" FROM read_intermediate_result('95_2'::text, 'binary'::citus_copy_format) intermediate_result("?column?" integer, "?column?_1" integer)
+DEBUG:  Plan 95 query after replacing subqueries and CTEs: SELECT u.x, u.y, test.y FROM ((SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('95_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u JOIN recursive_union.test USING (x)) ORDER BY u.x, u.y
+ x | y | y 
+---+---+---
+ 1 | 1 | 1
+ 2 | 2 | 2
+(2 rows)
+
+-- a join between a set operation and a generate_series which is pushdownable
+ SELECT * FROM ((SELECT * FROM test) UNION (SELECT * FROM test ORDER BY x)) u JOIN generate_series(1,10) x USING (x) ORDER BY 1,2;
+ x | y 
+---+---
+ 1 | 1
+ 2 | 2
+(2 rows)
+
+-- a join between a set operation and a generate_series which is not pushdownable due to EXCEPT
+ SELECT * FROM ((SELECT * FROM test) EXCEPT (SELECT * FROM test ORDER BY x)) u JOIN generate_series(1,10) x USING (x) ORDER BY 1,2;
+DEBUG:  generating subplan 100_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  generating subplan 100_2 for subquery SELECT x, y FROM recursive_union.test ORDER BY x
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 100_3 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('100_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) EXCEPT SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('100_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)
+DEBUG:  Plan 100 query after replacing subqueries and CTEs: SELECT u.x, u.y FROM ((SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('100_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u JOIN generate_series(1, 10) x(x) USING (x)) ORDER BY u.x, u.y
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+(0 rows)
+
+-- subqueries in WHERE clause with set operations fails due to the current limitaions of recursive planning IN WHERE clause
+SELECT * FROM ((SELECT * FROM test) UNION (SELECT * FROM test)) foo WHERE x IN (SELECT y FROM test);
+ERROR:  cannot pushdown the subquery since not all subqueries in the UNION have the partition column in the same position
+DETAIL:  Each leaf query of the UNION should return the partition column in the same position and all joins must be on the partition column
+-- subqueries in WHERE clause forced to be recursively planned
+SELECT * FROM ((SELECT * FROM test) UNION (SELECT * FROM test)) foo WHERE x IN (SELECT y FROM test ORDER BY 1 LIMIT 4) ORDER BY 1;
+DEBUG:  push down of limit count: 4
+DEBUG:  generating subplan 105_1 for subquery SELECT y FROM recursive_union.test ORDER BY y LIMIT 4
+DEBUG:  Plan 105 query after replacing subqueries and CTEs: SELECT x, y FROM (SELECT test.x, test.y FROM recursive_union.test UNION SELECT test.x, test.y FROM recursive_union.test) foo WHERE (x IN (SELECT intermediate_result.y FROM read_intermediate_result('105_1'::text, 'binary'::citus_copy_format) intermediate_result(y integer))) ORDER BY x
+ x | y 
+---+---
+ 1 | 1
+ 2 | 2
+(2 rows)
+
+-- now both the set operations and the sublink is recursively planned
+SELECT * FROM ((SELECT x,y FROM test) UNION (SELECT y,x FROM test)) foo WHERE x IN (SELECT y FROM test ORDER BY 1 LIMIT 4) ORDER BY 1;
+DEBUG:  push down of limit count: 4
+DEBUG:  generating subplan 107_1 for subquery SELECT y FROM recursive_union.test ORDER BY y LIMIT 4
+DEBUG:  generating subplan 107_2 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  generating subplan 107_3 for subquery SELECT y, x FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 107_4 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('107_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) UNION SELECT intermediate_result.y, intermediate_result.x FROM read_intermediate_result('107_3'::text, 'binary'::citus_copy_format) intermediate_result(y integer, x integer)
+DEBUG:  Plan 107 query after replacing subqueries and CTEs: SELECT x, y FROM (SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('107_4'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) foo WHERE (x IN (SELECT intermediate_result.y FROM read_intermediate_result('107_1'::text, 'binary'::citus_copy_format) intermediate_result(y integer))) ORDER BY x
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+ 1 | 1
+ 2 | 2
+(2 rows)
+
+-- set operations are recursively planned and not the sublink, thus should error out
+SELECT * FROM ((SELECT x,y FROM test) UNION (SELECT y,x FROM test)) foo WHERE x IN (SELECT y FROM test) ORDER BY 1;
+DEBUG:  generating subplan 112_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  generating subplan 112_2 for subquery SELECT y, x FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 112_3 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('112_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) UNION SELECT intermediate_result.y, intermediate_result.x FROM read_intermediate_result('112_2'::text, 'binary'::citus_copy_format) intermediate_result(y integer, x integer)
+DEBUG:  Plan 112 query after replacing subqueries and CTEs: SELECT x, y FROM (SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('112_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) foo WHERE (x IN (SELECT test.y FROM recursive_union.test)) ORDER BY x
+ERROR:  cannot pushdown the subquery
+DETAIL:  Complex subqueries and CTEs are not allowed in the FROM clause when the query has subqueries in the WHERE clause
+-- set operations works fine with pushdownable window functions
+SELECT x, y, rnk FROM (SELECT *, rank() OVER my_win as rnk FROM test WINDOW my_win AS (PARTITION BY x ORDER BY y DESC)) as foo
+UNION
+SELECT x, y, rnk FROM (SELECT *, rank() OVER my_win as rnk FROM test WINDOW my_win AS (PARTITION BY x ORDER BY y DESC)) as bar
+ORDER BY 1 DESC, 2 DESC, 3 DESC;
+DEBUG:  generating subplan 116_1 for subquery SELECT x, y, rnk FROM (SELECT test.x, test.y, rank() OVER my_win AS rnk FROM recursive_union.test WINDOW my_win AS (PARTITION BY test.x ORDER BY test.y DESC)) foo
+DEBUG:  generating subplan 116_2 for subquery SELECT x, y, rnk FROM (SELECT test.x, test.y, rank() OVER my_win AS rnk FROM recursive_union.test WINDOW my_win AS (PARTITION BY test.x ORDER BY test.y DESC)) bar
+DEBUG:  Plan 116 query after replacing subqueries and CTEs: SELECT intermediate_result.x, intermediate_result.y, intermediate_result.rnk FROM read_intermediate_result('116_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer, rnk bigint) UNION SELECT intermediate_result.x, intermediate_result.y, intermediate_result.rnk FROM read_intermediate_result('116_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer, rnk bigint) ORDER BY 1 DESC, 2 DESC, 3 DESC
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y | rnk 
+---+---+-----
+ 2 | 2 |   1
+ 1 | 1 |   1
+(2 rows)
+
+-- set operations errors out with non-pushdownable window functions
+SELECT x, y, rnk FROM (SELECT *, rank() OVER my_win as rnk FROM test WINDOW my_win AS (PARTITION BY y ORDER BY x DESC)) as foo
+UNION
+SELECT x, y, rnk FROM (SELECT *, rank() OVER my_win as rnk FROM test WINDOW my_win AS (PARTITION BY y ORDER BY x DESC)) as bar;
+ERROR:  could not run distributed query because the window function that is used cannot be pushed down
+HINT:  Window functions are supported in two ways. Either add an equality filter on the distributed tables' partition column or use the window functions inside a subquery with a PARTITION BY clause containing the distribution column
+-- other set operations in joins also cannot be pushed down
+SELECT * FROM ((SELECT * FROM test) EXCEPT (SELECT * FROM test ORDER BY x LIMIT 1)) u JOIN test USING (x) ORDER BY 1,2;
+DEBUG:  push down of limit count: 1
+DEBUG:  generating subplan 121_1 for subquery SELECT x, y FROM recursive_union.test ORDER BY x LIMIT 1
+DEBUG:  generating subplan 121_2 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 121_3 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('121_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) EXCEPT SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('121_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)
+DEBUG:  Plan 121 query after replacing subqueries and CTEs: SELECT u.x, u.y, test.y FROM ((SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('121_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u JOIN recursive_union.test USING (x)) ORDER BY u.x, u.y
+ x | y | y 
+---+---+---
+ 2 | 2 | 2
+(1 row)
+
+SELECT * FROM ((SELECT * FROM test) INTERSECT (SELECT * FROM test ORDER BY x LIMIT 1)) u LEFT JOIN test USING (x) ORDER BY 1,2;
+DEBUG:  push down of limit count: 1
+DEBUG:  generating subplan 125_1 for subquery SELECT x, y FROM recursive_union.test ORDER BY x LIMIT 1
+DEBUG:  generating subplan 125_2 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 125_3 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('125_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) INTERSECT SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('125_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)
+DEBUG:  Plan 125 query after replacing subqueries and CTEs: SELECT u.x, u.y, test.y FROM ((SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('125_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u LEFT JOIN recursive_union.test USING (x)) ORDER BY u.x, u.y
+ERROR:  cannot pushdown the subquery
+DETAIL:  Complex subqueries and CTEs cannot be in the outer part of the outer join
+-- distributed table in WHERE clause, but not FROM clause still disallowed
+SELECT * FROM ((SELECT * FROM test) UNION (SELECT * FROM ref WHERE a IN (SELECT x FROM test))) u ORDER BY 1,2;
+ERROR:  cannot pushdown the subquery
+DETAIL:  Reference tables are not allowed in FROM clause when the query has subqueries in WHERE clause
+-- subquery union in WHERE clause with partition column equality and implicit join is pushed down
+SELECT * FROM test a WHERE x IN (SELECT x FROM test b WHERE y = 1 UNION SELECT x FROM test c WHERE y = 2) ORDER BY 1,2;
+ x | y 
+---+---
+ 1 | 1
+ 2 | 2
+(2 rows)
+
+-- subquery union in WHERE clause with partition column equality, without implicit join on partition column
+SELECT * FROM test a WHERE x NOT IN (SELECT x FROM test b WHERE y = 1 UNION SELECT x FROM test c WHERE y = 2) ORDER BY 1,2;
+ERROR:  complex joins are only supported when all distributed tables are joined on their distribution columns with equal operator
+-- subquery union in WHERE clause without parition column equality is recursively planned
+SELECT * FROM test a WHERE x IN (SELECT x FROM test b UNION SELECT y FROM test c) ORDER BY 1,2;
+DEBUG:  generating subplan 133_1 for subquery SELECT x FROM recursive_union.test b
+DEBUG:  generating subplan 133_2 for subquery SELECT y FROM recursive_union.test c
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 133_3 for subquery SELECT intermediate_result.x FROM read_intermediate_result('133_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer) UNION SELECT intermediate_result.y FROM read_intermediate_result('133_2'::text, 'binary'::citus_copy_format) intermediate_result(y integer)
+DEBUG:  Plan 133 query after replacing subqueries and CTEs: SELECT x, y FROM recursive_union.test a WHERE (x IN (SELECT intermediate_result.x FROM read_intermediate_result('133_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer))) ORDER BY x, y
+ x | y 
+---+---
+ 1 | 1
+ 2 | 2
+(2 rows)
+
+-- correlated subquery with union in WHERE clause
+SELECT * FROM test a WHERE x IN (SELECT x FROM test b UNION SELECT y FROM test c WHERE a.x = c.x) ORDER BY 1,2;
+DEBUG:  generating subplan 137_1 for subquery SELECT x FROM recursive_union.test b
+DEBUG:  skipping recursive planning for the subquery since it contains references to outer queries
+DEBUG:  skipping recursive planning for the subquery since it contains references to outer queries
+DEBUG:  Plan 137 query after replacing subqueries and CTEs: SELECT x, y FROM recursive_union.test a WHERE (x IN (SELECT intermediate_result.x FROM read_intermediate_result('137_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer) UNION SELECT c.y FROM recursive_union.test c WHERE (a.x = c.x))) ORDER BY x, y
+DEBUG:  skipping recursive planning for the subquery since it contains references to outer queries
+DEBUG:  skipping recursive planning for the subquery since it contains references to outer queries
+ERROR:  complex joins are only supported when all distributed tables are joined on their distribution columns with equal operator
+-- force unions to be planned while subqueries are being planned
+SELECT * FROM ((SELECT * FROM test) UNION (SELECT * FROM test) ORDER BY 1,2 LIMIT 5) as foo ORDER BY 1 DESC LIMIT 3;
+DEBUG:  generating subplan 140_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  generating subplan 140_2 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  Plan 140 query after replacing subqueries and CTEs: SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('140_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) UNION SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('140_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) ORDER BY 1, 2 LIMIT 5
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 139_1 for subquery SELECT test.x, test.y FROM recursive_union.test UNION SELECT test.x, test.y FROM recursive_union.test ORDER BY 1, 2 LIMIT 5
+DEBUG:  Plan 139 query after replacing subqueries and CTEs: SELECT x, y FROM (SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('139_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) foo ORDER BY x DESC LIMIT 3
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x | y 
+---+---
+ 2 | 2
+ 1 | 1
+(2 rows)
+
+-- distinct and count distinct should work without any problems
+select count(DISTINCT t.x) FROM ((SELECT DISTINCT x FROM test) UNION (SELECT DISTINCT y FROM test)) as t(x) ORDER BY 1;
+DEBUG:  generating subplan 143_1 for subquery SELECT DISTINCT y FROM recursive_union.test
+DEBUG:  generating subplan 143_2 for subquery SELECT DISTINCT x FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 143_3 for subquery SELECT intermediate_result.x FROM read_intermediate_result('143_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer) UNION SELECT intermediate_result.y FROM read_intermediate_result('143_1'::text, 'binary'::citus_copy_format) intermediate_result(y integer)
+DEBUG:  Plan 143 query after replacing subqueries and CTEs: SELECT count(DISTINCT x) AS count FROM (SELECT intermediate_result.x FROM read_intermediate_result('143_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer)) t(x) ORDER BY (count(DISTINCT x))
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ count 
+-------
+     2
+(1 row)
+
+select count(DISTINCT t.x) FROM ((SELECT count(DISTINCT x) FROM test) UNION (SELECT count(DISTINCT y) FROM test)) as t(x) ORDER BY 1;
+DEBUG:  generating subplan 147_1 for subquery SELECT count(DISTINCT x) AS count FROM recursive_union.test
+DEBUG:  generating subplan 147_2 for subquery SELECT count(DISTINCT y) AS count FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 147_3 for subquery SELECT intermediate_result.count FROM read_intermediate_result('147_1'::text, 'binary'::citus_copy_format) intermediate_result(count bigint) UNION SELECT intermediate_result.count FROM read_intermediate_result('147_2'::text, 'binary'::citus_copy_format) intermediate_result(count bigint)
+DEBUG:  Plan 147 query after replacing subqueries and CTEs: SELECT count(DISTINCT x) AS count FROM (SELECT intermediate_result.count FROM read_intermediate_result('147_3'::text, 'binary'::citus_copy_format) intermediate_result(count bigint)) t(x) ORDER BY (count(DISTINCT x))
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ count 
+-------
+     1
+(1 row)
+
+-- other agg. distincts are also supported when group by includes partition key 
+select avg(DISTINCT t.x) FROM ((SELECT avg(DISTINCT y) FROM test GROUP BY x) UNION (SELECT avg(DISTINCT y) FROM test GROUP BY x)) as t(x) ORDER BY 1;
+DEBUG:  generating subplan 151_1 for subquery SELECT avg(DISTINCT y) AS avg FROM recursive_union.test GROUP BY x
+DEBUG:  generating subplan 151_2 for subquery SELECT avg(DISTINCT y) AS avg FROM recursive_union.test GROUP BY x
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 151_3 for subquery SELECT intermediate_result.avg FROM read_intermediate_result('151_1'::text, 'binary'::citus_copy_format) intermediate_result(avg numeric) UNION SELECT intermediate_result.avg FROM read_intermediate_result('151_2'::text, 'binary'::citus_copy_format) intermediate_result(avg numeric)
+DEBUG:  Plan 151 query after replacing subqueries and CTEs: SELECT avg(DISTINCT x) AS avg FROM (SELECT intermediate_result.avg FROM read_intermediate_result('151_3'::text, 'binary'::citus_copy_format) intermediate_result(avg numeric)) t(x) ORDER BY (avg(DISTINCT x))
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+          avg           
+------------------------
+ 1.50000000000000000000
+(1 row)
+
+-- other agg. distincts are not supported when group by doesn't include partition key 
+select count(DISTINCT t.x) FROM ((SELECT avg(DISTINCT y) FROM test GROUP BY y) UNION (SELECT avg(DISTINCT y) FROM test GROUP BY y)) as t(x) ORDER BY 1;
+ERROR:  cannot compute aggregate (distinct)
+DETAIL:  table partitioning is unsuitable for aggregate (distinct)
+-- one of the leaves is a repartition join
+SET citus.enable_repartition_joins TO ON;
+--  repartition is recursively planned before the set operation
+(SELECT x FROM test) INTERSECT (SELECT t1.x FROM test as t1, test as t2 WHERE t1.x = t2.y LIMIT 0) ORDER BY 1 DESC; 
+DEBUG:  push down of limit count: 0
+DEBUG:  join prunable for task partitionId 0 and 1
+DEBUG:  join prunable for task partitionId 0 and 2
+DEBUG:  join prunable for task partitionId 0 and 3
+DEBUG:  join prunable for task partitionId 1 and 0
+DEBUG:  join prunable for task partitionId 1 and 2
+DEBUG:  join prunable for task partitionId 1 and 3
+DEBUG:  join prunable for task partitionId 2 and 0
+DEBUG:  join prunable for task partitionId 2 and 1
+DEBUG:  join prunable for task partitionId 2 and 3
+DEBUG:  join prunable for task partitionId 3 and 0
+DEBUG:  join prunable for task partitionId 3 and 1
+DEBUG:  join prunable for task partitionId 3 and 2
+DEBUG:  pruning merge fetch taskId 1
+DETAIL:  Creating dependency on merge taskId 9
+DEBUG:  pruning merge fetch taskId 2
+DETAIL:  Creating dependency on merge taskId 9
+DEBUG:  pruning merge fetch taskId 4
+DETAIL:  Creating dependency on merge taskId 14
+DEBUG:  pruning merge fetch taskId 5
+DETAIL:  Creating dependency on merge taskId 14
+DEBUG:  pruning merge fetch taskId 7
+DETAIL:  Creating dependency on merge taskId 19
+DEBUG:  pruning merge fetch taskId 8
+DETAIL:  Creating dependency on merge taskId 19
+DEBUG:  pruning merge fetch taskId 10
+DETAIL:  Creating dependency on merge taskId 24
+DEBUG:  pruning merge fetch taskId 11
+DETAIL:  Creating dependency on merge taskId 24
+DEBUG:  cannot use real time executor with repartition jobs
+HINT:  Since you enabled citus.enable_repartition_joins Citus chose to use task-tracker.
+DEBUG:  generating subplan 157_1 for subquery SELECT t1.x FROM recursive_union.test t1, recursive_union.test t2 WHERE (t1.x = t2.y) LIMIT 0
+DEBUG:  generating subplan 157_2 for subquery SELECT x FROM recursive_union.test
+DEBUG:  Plan 157 query after replacing subqueries and CTEs: SELECT intermediate_result.x FROM read_intermediate_result('157_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer) INTERSECT SELECT intermediate_result.x FROM read_intermediate_result('157_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer) ORDER BY 1 DESC
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x 
+---
+(0 rows)
+
+--  repartition is recursively planned with the set operation
+(SELECT x FROM test) INTERSECT (SELECT t1.x FROM test as t1, test as t2 WHERE t1.x = t2.y) ORDER BY 1 DESC;
+DEBUG:  generating subplan 160_1 for subquery SELECT x FROM recursive_union.test
+DEBUG:  join prunable for task partitionId 0 and 1
+DEBUG:  join prunable for task partitionId 0 and 2
+DEBUG:  join prunable for task partitionId 0 and 3
+DEBUG:  join prunable for task partitionId 1 and 0
+DEBUG:  join prunable for task partitionId 1 and 2
+DEBUG:  join prunable for task partitionId 1 and 3
+DEBUG:  join prunable for task partitionId 2 and 0
+DEBUG:  join prunable for task partitionId 2 and 1
+DEBUG:  join prunable for task partitionId 2 and 3
+DEBUG:  join prunable for task partitionId 3 and 0
+DEBUG:  join prunable for task partitionId 3 and 1
+DEBUG:  join prunable for task partitionId 3 and 2
+DEBUG:  pruning merge fetch taskId 1
+DETAIL:  Creating dependency on merge taskId 9
+DEBUG:  pruning merge fetch taskId 2
+DETAIL:  Creating dependency on merge taskId 9
+DEBUG:  pruning merge fetch taskId 4
+DETAIL:  Creating dependency on merge taskId 14
+DEBUG:  pruning merge fetch taskId 5
+DETAIL:  Creating dependency on merge taskId 14
+DEBUG:  pruning merge fetch taskId 7
+DETAIL:  Creating dependency on merge taskId 19
+DEBUG:  pruning merge fetch taskId 8
+DETAIL:  Creating dependency on merge taskId 19
+DEBUG:  pruning merge fetch taskId 10
+DETAIL:  Creating dependency on merge taskId 24
+DEBUG:  pruning merge fetch taskId 11
+DETAIL:  Creating dependency on merge taskId 24
+DEBUG:  cannot use real time executor with repartition jobs
+HINT:  Since you enabled citus.enable_repartition_joins Citus chose to use task-tracker.
+DEBUG:  generating subplan 160_2 for subquery SELECT t1.x FROM recursive_union.test t1, recursive_union.test t2 WHERE (t1.x = t2.y)
+DEBUG:  Plan 160 query after replacing subqueries and CTEs: SELECT intermediate_result.x FROM read_intermediate_result('160_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer) INTERSECT SELECT intermediate_result.x FROM read_intermediate_result('160_2'::text, 'binary'::citus_copy_format) intermediate_result(x integer) ORDER BY 1 DESC
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x 
+---
+ 2
+ 1
+(2 rows)
+
+SET citus.enable_repartition_joins TO OFF;
+-- this should be recursively planned
+CREATE VIEW set_view_recursive AS (SELECT y FROM test) UNION (SELECT y FROM test);
+SELECT * FROM set_view_recursive ORDER BY 1 DESC;
+DEBUG:  generating subplan 163_1 for subquery SELECT y FROM recursive_union.test
+DEBUG:  generating subplan 163_2 for subquery SELECT y FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 163_3 for subquery SELECT intermediate_result.y FROM read_intermediate_result('163_1'::text, 'binary'::citus_copy_format) intermediate_result(y integer) UNION SELECT intermediate_result.y FROM read_intermediate_result('163_2'::text, 'binary'::citus_copy_format) intermediate_result(y integer)
+DEBUG:  Plan 163 query after replacing subqueries and CTEs: SELECT y FROM (SELECT intermediate_result.y FROM read_intermediate_result('163_3'::text, 'binary'::citus_copy_format) intermediate_result(y integer)) set_view_recursive ORDER BY y DESC
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ y 
+---
+ 2
+ 1
+(2 rows)
+
+-- this should be pushed down
+CREATE VIEW set_view_pushdown AS (SELECT x FROM test) UNION (SELECT x FROM test);
+SELECT * FROM set_view_pushdown ORDER BY 1 DESC;
+ x 
+---
+ 2
+ 1
+(2 rows)
+
+-- this should be recursively planned
+CREATE VIEW set_view_recursive_second AS SELECT u.x, test.y FROM ((SELECT x, y FROM test) UNION (SELECT 1, 1 FROM test)) u JOIN test USING (x) ORDER BY 1,2;
+SELECT * FROM set_view_recursive_second;
+DEBUG:  generating subplan 168_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  generating subplan 168_2 for subquery SELECT 1, 1 FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 168_3 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('168_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) UNION SELECT intermediate_result."?column?", intermediate_result."?column?_1" AS "?column?" FROM read_intermediate_result('168_2'::text, 'binary'::citus_copy_format) intermediate_result("?column?" integer, "?column?_1" integer)
+DEBUG:  Plan 168 query after replacing subqueries and CTEs: SELECT x, y FROM (SELECT u.x, test.y FROM ((SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('168_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u JOIN recursive_union.test USING (x)) ORDER BY u.x, test.y) set_view_recursive_second
+ x | y 
+---+---
+ 1 | 1
+ 2 | 2
+(2 rows)
+
+-- this should create lots of recursive calls since both views and set operations lead to recursive plans :) 
+((SELECT x FROM set_view_recursive_second) INTERSECT (SELECT * FROM set_view_recursive)) EXCEPT (SELECT * FROM set_view_pushdown);
+DEBUG:  generating subplan 172_1 for subquery SELECT x, y FROM recursive_union.test
+DEBUG:  generating subplan 172_2 for subquery SELECT 1, 1 FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 172_3 for subquery SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('172_1'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer) UNION SELECT intermediate_result."?column?", intermediate_result."?column?_1" AS "?column?" FROM read_intermediate_result('172_2'::text, 'binary'::citus_copy_format) intermediate_result("?column?" integer, "?column?_1" integer)
+DEBUG:  generating subplan 172_4 for subquery SELECT y FROM recursive_union.test
+DEBUG:  generating subplan 172_5 for subquery SELECT y FROM recursive_union.test
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+DEBUG:  generating subplan 172_6 for subquery SELECT intermediate_result.y FROM read_intermediate_result('172_4'::text, 'binary'::citus_copy_format) intermediate_result(y integer) UNION SELECT intermediate_result.y FROM read_intermediate_result('172_5'::text, 'binary'::citus_copy_format) intermediate_result(y integer)
+DEBUG:  generating subplan 172_7 for subquery SELECT x FROM (SELECT u.x, test.y FROM ((SELECT intermediate_result.x, intermediate_result.y FROM read_intermediate_result('172_3'::text, 'binary'::citus_copy_format) intermediate_result(x integer, y integer)) u JOIN recursive_union.test USING (x)) ORDER BY u.x, test.y) set_view_recursive_second
+DEBUG:  generating subplan 172_8 for subquery SELECT x FROM (SELECT test.x FROM recursive_union.test UNION SELECT test.x FROM recursive_union.test) set_view_pushdown
+DEBUG:  Plan 172 query after replacing subqueries and CTEs: (SELECT intermediate_result.x FROM read_intermediate_result('172_7'::text, 'binary'::citus_copy_format) intermediate_result(x integer) INTERSECT SELECT set_view_recursive.y FROM (SELECT intermediate_result.y FROM read_intermediate_result('172_6'::text, 'binary'::citus_copy_format) intermediate_result(y integer)) set_view_recursive) EXCEPT SELECT intermediate_result.x FROM read_intermediate_result('172_8'::text, 'binary'::citus_copy_format) intermediate_result(x integer)
+DEBUG:  Creating router plan
+DEBUG:  Plan is router executable
+ x 
+---
+(0 rows)
+
+RESET client_min_messages;
+DROP SCHEMA recursive_union CASCADE;
+NOTICE:  drop cascades to 5 other objects
+DETAIL:  drop cascades to table test
+drop cascades to table ref
+drop cascades to view set_view_recursive
+drop cascades to view set_view_pushdown
+drop cascades to view set_view_recursive_second

src/test/regress/expected/with_basics.out

@@ -563,7 +563,7 @@ LIMIT
        1 |  90
 (5 rows)
 
--- SELECT * FROM (SELECT * FROM cte UNION SELECT * FROM distributed_table) a; should error out
+-- SELECT * FROM (SELECT * FROM cte UNION SELECT * FROM distributed_table) a; should work
 WITH cte AS (
 	SELECT * FROM users_table
 )
@@ -574,8 +574,20 @@ ORDER BY
 	1,2,3,4,5,6
 LIMIT 
 	10;
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ user_id |              time               | value_1 | value_2 | value_3 | value_4 
-HINT:  Consider using an equality filter on the distributed table's partition column.
+---------+---------------------------------+---------+---------+---------+---------
+       1 | Wed Nov 22 18:49:42.327403 2017 |       3 |       2 |       1 |        
+       1 | Wed Nov 22 19:03:01.772353 2017 |       4 |       1 |       2 |        
+       1 | Wed Nov 22 19:07:03.846437 2017 |       1 |       2 |       5 |        
+       1 | Wed Nov 22 20:56:21.122638 2017 |       2 |       4 |       4 |        
+       1 | Wed Nov 22 21:06:57.457147 2017 |       4 |       3 |       2 |        
+       1 | Wed Nov 22 21:47:04.188168 2017 |       4 |       2 |       0 |        
+       1 | Wed Nov 22 22:51:43.132261 2017 |       4 |       0 |       3 |        
+       1 | Wed Nov 22 23:22:09.957743 2017 |       1 |       1 |       1 |        
+       1 | Thu Nov 23 00:42:37.237615 2017 |       2 |       4 |       3 |        
+       1 | Thu Nov 23 02:59:23.620864 2017 |       4 |       5 |       4 |        
+(10 rows)
+
 SELECT * FROM (
 	SELECT * FROM (WITH cte AS (
 			SELECT * FROM users_table
@@ -586,8 +598,20 @@ ORDER BY
 1,2,3,4,5,6
 LIMIT 
 10;
-ERROR:  could not run distributed query with UNION, INTERSECT, or EXCEPT
+ user_id |              time               | value_1 | value_2 | value_3 | value_4 
-HINT:  Consider using an equality filter on the distributed table's partition column.
+---------+---------------------------------+---------+---------+---------+---------
+       1 | Wed Nov 22 18:49:42.327403 2017 |       3 |       2 |       1 |        
+       1 | Wed Nov 22 19:03:01.772353 2017 |       4 |       1 |       2 |        
+       1 | Wed Nov 22 19:07:03.846437 2017 |       1 |       2 |       5 |        
+       1 | Wed Nov 22 20:56:21.122638 2017 |       2 |       4 |       4 |        
+       1 | Wed Nov 22 21:06:57.457147 2017 |       4 |       3 |       2 |        
+       1 | Wed Nov 22 21:47:04.188168 2017 |       4 |       2 |       0 |        
+       1 | Wed Nov 22 22:51:43.132261 2017 |       4 |       0 |       3 |        
+       1 | Wed Nov 22 23:22:09.957743 2017 |       1 |       1 |       1 |        
+       1 | Thu Nov 23 00:42:37.237615 2017 |       2 |       4 |       3 |        
+       1 | Thu Nov 23 02:59:23.620864 2017 |       4 |       5 |       4 |        
+(10 rows)
+
 -- SELECT * FROM (SELECT * FROM cte UNION SELECT * FROM cte) a; should work
 WITH cte AS (
 	SELECT * FROM users_table WHERE user_id IN (1, 2)

src/test/regress/expected/with_set_operations.out

@@ -0,0 +1,417 @@
+-- ===================================================================
+-- test recursive planning functionality with Set Operations and CTEs
+-- ===================================================================
+SET client_min_messages TO DEBUG1;
+-- use ctes inside unions on the top level
+WITH 
+cte_1 AS (SELECT user_id FROM users_table),
+cte_2 AS (SELECT user_id FROM events_table)
+(SELECT * FROM cte_1) UNION (SELECT * FROM cte_2)
+ORDER BY 1 DESC;
+DEBUG:  generating subplan 1_1 for CTE cte_1: SELECT user_id FROM public.users_table
+DEBUG:  generating subplan 1_2 for CTE cte_2: SELECT user_id FROM public.events_table
+DEBUG:  Plan 1 query after replacing subqueries and CTEs: SELECT cte_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('1_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_1 UNION SELECT cte_2.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('1_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_2 ORDER BY 1 DESC
+ user_id 
+---------
+       6
+       5
+       4
+       3
+       2
+       1
+(6 rows)
+
+-- use ctes inside unions in a subquery
+WITH 
+cte_1 AS (SELECT user_id FROM users_table),
+cte_2 AS (SELECT user_id FROM events_table)
+SELECT 
+	count(*) 
+FROM (
+		(SELECT * FROM cte_1) UNION (SELECT * FROM cte_2)
+	) as foo;
+DEBUG:  generating subplan 4_1 for CTE cte_1: SELECT user_id FROM public.users_table
+DEBUG:  generating subplan 4_2 for CTE cte_2: SELECT user_id FROM public.events_table
+DEBUG:  generating subplan 4_3 for subquery SELECT cte_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('4_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_1 UNION SELECT cte_2.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('4_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_2
+DEBUG:  Plan 4 query after replacing subqueries and CTEs: SELECT count(*) AS count FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('4_3'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) foo
+ count 
+-------
+     6
+(1 row)
+
+-- cte with unions of other ctes
+WITH 
+cte_1 AS (SELECT user_id FROM users_table),
+cte_2 AS (SELECT user_id FROM events_table),
+cte_3 AS ((SELECT * FROM cte_1) UNION (SELECT * FROM cte_2))
+SELECT * FROM cte_3 ORDER BY 1 DESC;
+DEBUG:  generating subplan 8_1 for CTE cte_1: SELECT user_id FROM public.users_table
+DEBUG:  generating subplan 8_2 for CTE cte_2: SELECT user_id FROM public.events_table
+DEBUG:  generating subplan 8_3 for CTE cte_3: SELECT cte_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('8_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_1 UNION SELECT cte_2.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('8_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_2
+DEBUG:  Plan 8 query after replacing subqueries and CTEs: SELECT user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('8_3'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_3 ORDER BY user_id DESC
+ user_id 
+---------
+       6
+       5
+       4
+       3
+       2
+       1
+(6 rows)
+
+-- cte with unions of distributed table
+WITH 
+cte_1 AS ((SELECT user_id FROM users_table) UNION (SELECT user_id FROM users_table))
+SELECT * FROM cte_1 ORDER BY 1 DESC;
+DEBUG:  generating subplan 12_1 for CTE cte_1: SELECT users_table.user_id FROM public.users_table UNION SELECT users_table.user_id FROM public.users_table
+DEBUG:  generating subplan 13_1 for subquery SELECT user_id FROM public.users_table
+DEBUG:  generating subplan 13_2 for subquery SELECT user_id FROM public.users_table
+DEBUG:  Plan 13 query after replacing subqueries and CTEs: SELECT intermediate_result.user_id FROM read_intermediate_result('13_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer) UNION SELECT intermediate_result.user_id FROM read_intermediate_result('13_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)
+DEBUG:  Plan 12 query after replacing subqueries and CTEs: SELECT user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('12_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_1 ORDER BY user_id DESC
+ user_id 
+---------
+       6
+       5
+       4
+       3
+       2
+       1
+(6 rows)
+
+-- cte with unions of tables is intersected with another query
+WITH 
+cte_1 AS ((SELECT user_id FROM users_table) UNION (SELECT user_id FROM users_table))
+(SELECT * FROM cte_1) INTERSECT (SELECT user_id FROM users_table) ORDER BY 1 DESC;
+DEBUG:  generating subplan 16_1 for CTE cte_1: SELECT users_table.user_id FROM public.users_table UNION SELECT users_table.user_id FROM public.users_table
+DEBUG:  generating subplan 17_1 for subquery SELECT user_id FROM public.users_table
+DEBUG:  generating subplan 17_2 for subquery SELECT user_id FROM public.users_table
+DEBUG:  Plan 17 query after replacing subqueries and CTEs: SELECT intermediate_result.user_id FROM read_intermediate_result('17_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer) UNION SELECT intermediate_result.user_id FROM read_intermediate_result('17_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)
+DEBUG:  generating subplan 16_2 for subquery SELECT user_id FROM public.users_table
+DEBUG:  Plan 16 query after replacing subqueries and CTEs: SELECT cte_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('16_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_1 INTERSECT SELECT intermediate_result.user_id FROM read_intermediate_result('16_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer) ORDER BY 1 DESC
+ user_id 
+---------
+       6
+       5
+       4
+       3
+       2
+       1
+(6 rows)
+
+-- cte with unions of tables is intersected with another query that involves except
+WITH 
+cte_1 AS ((SELECT user_id FROM users_table) UNION (SELECT user_id FROM users_table))
+(SELECT * FROM cte_1) 
+	INTERSECT 
+((SELECT user_id FROM events_table WHERE user_id < 3) EXCEPT (SELECT user_id FROM users_table WHERE user_id > 4)) ORDER BY 1 DESC;
+DEBUG:  generating subplan 21_1 for CTE cte_1: SELECT users_table.user_id FROM public.users_table UNION SELECT users_table.user_id FROM public.users_table
+DEBUG:  generating subplan 22_1 for subquery SELECT user_id FROM public.users_table
+DEBUG:  generating subplan 22_2 for subquery SELECT user_id FROM public.users_table
+DEBUG:  Plan 22 query after replacing subqueries and CTEs: SELECT intermediate_result.user_id FROM read_intermediate_result('22_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer) UNION SELECT intermediate_result.user_id FROM read_intermediate_result('22_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)
+DEBUG:  generating subplan 21_2 for subquery SELECT user_id FROM public.events_table WHERE (user_id < 3)
+DEBUG:  generating subplan 21_3 for subquery SELECT user_id FROM public.users_table WHERE (user_id > 4)
+DEBUG:  Plan 21 query after replacing subqueries and CTEs: SELECT cte_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('21_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_1 INTERSECT (SELECT intermediate_result.user_id FROM read_intermediate_result('21_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer) EXCEPT SELECT intermediate_result.user_id FROM read_intermediate_result('21_3'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) ORDER BY 1 DESC
+ user_id 
+---------
+       2
+       1
+(2 rows)
+
+-- CTE inside a top level EXCEPT
+(WITH cte_1 AS (SELECT user_id FROM events_table WHERE user_id < 3) SELECT * FROM cte_1) INTERSECT (SELECT user_id FROM users_table) ORDER BY 1;   
+DEBUG:  generating subplan 27_1 for CTE cte_1: SELECT user_id FROM public.events_table WHERE (user_id < 3)
+DEBUG:  generating subplan 27_2 for subquery SELECT user_id FROM public.users_table
+DEBUG:  Plan 27 query after replacing subqueries and CTEs: SELECT cte_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('27_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_1 INTERSECT SELECT intermediate_result.user_id FROM read_intermediate_result('27_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer) ORDER BY 1
+ user_id 
+---------
+       1
+       2
+(2 rows)
+
+-- INTERSECT inside a CTE, which is inside a subquery
+SELECT 
+	DISTINCT users_table.user_id 
+FROM 
+	users_table, 
+	(WITH cte_1 AS (SELECT user_id FROM events_table WHERE user_id < 3 INTERSECT 
+					SELECT user_id FROM events_table WHERE user_id < 2) 
+	 SELECT * FROM cte_1) as foo
+WHERE
+	users_table.user_id = foo.user_id
+ORDER BY 1 DESC;
+DEBUG:  generating subplan 30_1 for CTE cte_1: SELECT events_table.user_id FROM public.events_table WHERE (events_table.user_id < 3) INTERSECT SELECT events_table.user_id FROM public.events_table WHERE (events_table.user_id < 2)
+DEBUG:  generating subplan 31_1 for subquery SELECT user_id FROM public.events_table WHERE (user_id < 3)
+DEBUG:  generating subplan 31_2 for subquery SELECT user_id FROM public.events_table WHERE (user_id < 2)
+DEBUG:  Plan 31 query after replacing subqueries and CTEs: SELECT intermediate_result.user_id FROM read_intermediate_result('31_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer) INTERSECT SELECT intermediate_result.user_id FROM read_intermediate_result('31_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)
+DEBUG:  Plan 30 query after replacing subqueries and CTEs: SELECT DISTINCT users_table.user_id FROM public.users_table, (SELECT cte_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('30_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_1) foo WHERE (users_table.user_id = foo.user_id) ORDER BY users_table.user_id DESC
+ user_id 
+---------
+       1
+(1 row)
+
+-- UNION is created via outputs of CTEs, which is inside a subquery
+-- and the subquery is joined with a distributed table
+SELECT 
+	count(*) 
+FROM 
+	events_table,
+	(
+		WITH 
+		cte_1 AS (SELECT user_id FROM users_table),
+		cte_2 AS (SELECT user_id FROM events_table)
+		(SELECT * FROM cte_1) UNION (SELECT * FROM cte_2)
+	) as foo
+WHERE foo.user_id = events_table.event_type;
+DEBUG:  generating subplan 34_1 for CTE cte_1: SELECT user_id FROM public.users_table
+DEBUG:  generating subplan 34_2 for CTE cte_2: SELECT user_id FROM public.events_table
+DEBUG:  generating subplan 34_3 for subquery SELECT cte_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('34_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_1 UNION SELECT cte_2.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('34_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_2
+DEBUG:  Plan 34 query after replacing subqueries and CTEs: SELECT count(*) AS count FROM public.events_table, (SELECT intermediate_result.user_id FROM read_intermediate_result('34_3'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) foo WHERE (foo.user_id = events_table.event_type)
+ count 
+-------
+    95
+(1 row)
+
+-- joins inside unions that are safe to pushdown
+(SELECT DISTINCT events_table.user_id FROM users_table, events_table WHERE users_table.user_id = events_table.user_id )
+INTERSECT
+(SELECT DISTINCT events_table.user_id FROM users_table, events_table WHERE users_table.user_id = events_table.user_id )
+ORDER BY 1 DESC;
+DEBUG:  generating subplan 38_1 for subquery SELECT DISTINCT events_table.user_id FROM public.users_table, public.events_table WHERE (users_table.user_id = events_table.user_id)
+DEBUG:  generating subplan 38_2 for subquery SELECT DISTINCT events_table.user_id FROM public.users_table, public.events_table WHERE (users_table.user_id = events_table.user_id)
+DEBUG:  Plan 38 query after replacing subqueries and CTEs: SELECT intermediate_result.user_id FROM read_intermediate_result('38_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer) INTERSECT SELECT intermediate_result.user_id FROM read_intermediate_result('38_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer) ORDER BY 1 DESC
+ user_id 
+---------
+       6
+       5
+       4
+       3
+       2
+       1
+(6 rows)
+
+-- joins inside unions that are not safe to pushdown
+(SELECT DISTINCT events_table.user_id FROM users_table, events_table WHERE users_table.user_id = events_table.user_id LIMIT 10)
+INTERSECT
+(SELECT DISTINCT events_table.user_id FROM users_table, events_table WHERE users_table.user_id = events_table.user_id LIMIT 10)
+ORDER BY 1 DESC;
+DEBUG:  push down of limit count: 10
+DEBUG:  generating subplan 41_1 for subquery SELECT DISTINCT events_table.user_id FROM public.users_table, public.events_table WHERE (users_table.user_id = events_table.user_id) LIMIT 10
+DEBUG:  push down of limit count: 10
+DEBUG:  generating subplan 41_2 for subquery SELECT DISTINCT events_table.user_id FROM public.users_table, public.events_table WHERE (users_table.user_id = events_table.user_id) LIMIT 10
+DEBUG:  Plan 41 query after replacing subqueries and CTEs: SELECT intermediate_result.user_id FROM read_intermediate_result('41_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer) INTERSECT SELECT intermediate_result.user_id FROM read_intermediate_result('41_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer) ORDER BY 1 DESC
+ user_id 
+---------
+       6
+       5
+       4
+       3
+       2
+       1
+(6 rows)
+
+-- joins inside unions that are not safe to pushdown inside a subquery
+SELECT 
+	count(*) 
+FROM 
+	(SELECT DISTINCT value_2 FROM events_table) as events_table,
+	(WITH foo AS 
+		((SELECT DISTINCT events_table.user_id FROM users_table, events_table WHERE users_table.user_id = events_table.user_id )
+	 	INTERSECT
+		(SELECT DISTINCT events_table.user_id FROM users_table, events_table WHERE users_table.user_id = events_table.user_id LIMIT 10)) 
+	 SELECT * FROM foo) 
+	as foo
+WHERE 
+	foo.user_id = events_table.value_2;
+DEBUG:  generating subplan 44_1 for subquery SELECT DISTINCT value_2 FROM public.events_table
+DEBUG:  generating subplan 44_2 for CTE foo: SELECT DISTINCT events_table.user_id FROM public.users_table, public.events_table WHERE (users_table.user_id = events_table.user_id) INTERSECT (SELECT DISTINCT events_table.user_id FROM public.users_table, public.events_table WHERE (users_table.user_id = events_table.user_id) LIMIT 10)
+DEBUG:  push down of limit count: 10
+DEBUG:  generating subplan 46_1 for subquery SELECT DISTINCT events_table.user_id FROM public.users_table, public.events_table WHERE (users_table.user_id = events_table.user_id) LIMIT 10
+DEBUG:  generating subplan 46_2 for subquery SELECT DISTINCT events_table.user_id FROM public.users_table, public.events_table WHERE (users_table.user_id = events_table.user_id)
+DEBUG:  Plan 46 query after replacing subqueries and CTEs: SELECT intermediate_result.user_id FROM read_intermediate_result('46_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer) INTERSECT SELECT intermediate_result.user_id FROM read_intermediate_result('46_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)
+DEBUG:  Plan 44 query after replacing subqueries and CTEs: SELECT count(*) AS count FROM (SELECT intermediate_result.value_2 FROM read_intermediate_result('44_1'::text, 'binary'::citus_copy_format) intermediate_result(value_2 integer)) events_table, (SELECT foo_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('44_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) foo_1) foo WHERE (foo.user_id = events_table.value_2)
+ count 
+-------
+     5
+(1 row)
+
+-- joins inside unions some safe to pushdown
+SELECT 
+	count(*) 
+FROM 
+	(WITH events_table AS (SELECT DISTINCT user_id FROM events_table) SELECT * FROM events_table) as events_table,
+	((SELECT DISTINCT events_table.user_id FROM users_table, events_table WHERE users_table.user_id = events_table.user_id )
+	INTERSECT
+	(SELECT DISTINCT events_table.user_id FROM users_table, events_table WHERE users_table.user_id = events_table.user_id LIMIT 10)) as foo
+WHERE 
+	foo.user_id = events_table.user_id;
+DEBUG:  generating subplan 49_1 for CTE events_table: SELECT DISTINCT user_id FROM public.events_table
+DEBUG:  push down of limit count: 10
+DEBUG:  generating subplan 49_2 for subquery SELECT DISTINCT events_table.user_id FROM public.users_table, public.events_table WHERE (users_table.user_id = events_table.user_id) LIMIT 10
+DEBUG:  generating subplan 49_3 for subquery SELECT DISTINCT events_table.user_id FROM public.users_table, public.events_table WHERE (users_table.user_id = events_table.user_id)
+DEBUG:  generating subplan 49_4 for subquery SELECT intermediate_result.user_id FROM read_intermediate_result('49_3'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer) INTERSECT SELECT intermediate_result.user_id FROM read_intermediate_result('49_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)
+DEBUG:  Plan 49 query after replacing subqueries and CTEs: SELECT count(*) AS count FROM (SELECT events_table_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('49_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) events_table_1) events_table, (SELECT intermediate_result.user_id FROM read_intermediate_result('49_4'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) foo WHERE (foo.user_id = events_table.user_id)
+ count 
+-------
+     6
+(1 row)
+
+-- CTE inside unions
+(WITH cte_1 AS (SELECT user_id FROM users_table) SELECT * FROM cte_1) UNION 
+(WITH cte_1 AS (SELECT user_id FROM users_table) SELECT * FROM cte_1) ORDER BY 1 DESC; 
+DEBUG:  generating subplan 54_1 for CTE cte_1: SELECT user_id FROM public.users_table
+DEBUG:  generating subplan 54_2 for CTE cte_1: SELECT user_id FROM public.users_table
+DEBUG:  Plan 54 query after replacing subqueries and CTEs: SELECT cte_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('54_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_1 UNION SELECT cte_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('54_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_1 ORDER BY 1 DESC
+ user_id 
+---------
+       6
+       5
+       4
+       3
+       2
+       1
+(6 rows)
+
+-- more complex CTEs inside unions
+SELECT
+	count(*)
+FROM
+	(
+		(WITH cte_1 AS (SELECT user_id FROM users_table) SELECT * FROM cte_1) UNION 
+		(WITH cte_1 AS (SELECT user_id FROM users_table) SELECT * FROM cte_1)
+	) as foo,
+	users_table
+	WHERE users_table.value_2 = foo.user_id;
+DEBUG:  generating subplan 57_1 for CTE cte_1: SELECT user_id FROM public.users_table
+DEBUG:  generating subplan 57_2 for CTE cte_1: SELECT user_id FROM public.users_table
+DEBUG:  generating subplan 57_3 for subquery SELECT cte_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('57_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_1 UNION SELECT cte_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('57_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_1
+DEBUG:  Plan 57 query after replacing subqueries and CTEs: SELECT count(*) AS count FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('57_3'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) foo, public.users_table WHERE (users_table.value_2 = foo.user_id)
+ count 
+-------
+    92
+(1 row)
+
+-- CTEs with less alias than the input subquery
+(WITH cte_1(x) AS (SELECT user_id, value_2 FROM users_table) SELECT * FROM cte_1) UNION 
+(WITH cte_1(x) AS (SELECT user_id, value_2 FROM users_table) SELECT * FROM cte_1) ORDER BY 1 DESC, 2 DESC LIMIT 5;
+DEBUG:  generating subplan 61_1 for CTE cte_1: SELECT user_id, value_2 FROM public.users_table
+DEBUG:  generating subplan 61_2 for CTE cte_1: SELECT user_id, value_2 FROM public.users_table
+DEBUG:  Plan 61 query after replacing subqueries and CTEs: SELECT cte_1.x, cte_1.value_2 FROM (SELECT intermediate_result.user_id AS x, intermediate_result.value_2 FROM read_intermediate_result('61_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer, value_2 integer)) cte_1 UNION SELECT cte_1.x, cte_1.value_2 FROM (SELECT intermediate_result.user_id AS x, intermediate_result.value_2 FROM read_intermediate_result('61_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer, value_2 integer)) cte_1 ORDER BY 1 DESC, 2 DESC LIMIT 5
+ x | value_2 
+---+---------
+ 6 |       4
+ 6 |       3
+ 6 |       2
+ 6 |       1
+ 6 |       0
+(5 rows)
+
+-- simple subqueries in WHERE with unions
+SELECT 
+	count(*)
+FROM
+	users_table
+WHERE
+	value_2 IN
+	(
+		WITH cte_1 AS
+		(
+			(SELECT user_id FROM users_table)
+			UNION
+		 	(SELECT user_id FROM events_table)
+		 ) SELECT DISTINCT user_id FROM cte_1
+)
+ORDER BY 1 DESC;
+DEBUG:  generating subplan 64_1 for CTE cte_1: SELECT users_table.user_id FROM public.users_table UNION SELECT events_table.user_id FROM public.events_table
+DEBUG:  generating subplan 65_1 for subquery SELECT user_id FROM public.users_table
+DEBUG:  generating subplan 65_2 for subquery SELECT user_id FROM public.events_table
+DEBUG:  Plan 65 query after replacing subqueries and CTEs: SELECT intermediate_result.user_id FROM read_intermediate_result('65_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer) UNION SELECT intermediate_result.user_id FROM read_intermediate_result('65_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)
+DEBUG:  Plan 64 query after replacing subqueries and CTEs: SELECT count(*) AS count FROM public.users_table WHERE (value_2 IN (SELECT DISTINCT cte_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('64_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_1)) ORDER BY (count(*)) DESC
+ count 
+-------
+    92
+(1 row)
+
+-- simple subqueries in WHERE with unions and ctes
+SELECT 
+	count(*)
+FROM
+	users_table
+WHERE
+	value_2 IN
+	(
+		WITH 
+		cte_1 AS (SELECT user_id FROM users_table),
+		cte_2 AS (SELECT user_id FROM events_table)
+		(SELECT * FROM cte_1) UNION (SELECT * FROM cte_2)
+)
+ORDER BY 1 DESC;
+DEBUG:  generating subplan 68_1 for CTE cte_1: SELECT user_id FROM public.users_table
+DEBUG:  generating subplan 68_2 for CTE cte_2: SELECT user_id FROM public.events_table
+DEBUG:  generating subplan 68_3 for subquery SELECT cte_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('68_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_1 UNION SELECT cte_2.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('68_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_2
+DEBUG:  Plan 68 query after replacing subqueries and CTEs: SELECT count(*) AS count FROM public.users_table WHERE (value_2 IN (SELECT intermediate_result.user_id FROM read_intermediate_result('68_3'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer))) ORDER BY (count(*)) DESC
+ count 
+-------
+    92
+(1 row)
+
+-- unions and ctes inside subqueries in where clause with a pushdownable correlated subquery
+SELECT 
+	DISTINCT user_id 
+FROM 
+	events_table 
+WHERE 
+	event_type IN 
+(
+	SELECT
+		users_table.user_id
+	FROM
+		(
+			(WITH cte_1 AS (SELECT user_id FROM users_table) SELECT * FROM cte_1) UNION 
+			(WITH cte_1 AS (SELECT user_id FROM users_table) SELECT * FROM cte_1)
+		) as foo,
+		users_table
+		WHERE users_table.value_2 = foo.user_id  AND events_table.user_id = users_table.user_id
+)
+ORDER BY 1 DESC;
+DEBUG:  generating subplan 72_1 for CTE cte_1: SELECT user_id FROM public.users_table
+DEBUG:  generating subplan 72_2 for CTE cte_1: SELECT user_id FROM public.users_table
+DEBUG:  generating subplan 72_3 for subquery SELECT cte_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('72_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_1 UNION SELECT cte_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('72_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_1
+DEBUG:  Plan 72 query after replacing subqueries and CTEs: SELECT DISTINCT user_id FROM public.events_table WHERE (event_type IN (SELECT users_table.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('72_3'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) foo, public.users_table WHERE ((users_table.value_2 = foo.user_id) AND (events_table.user_id = users_table.user_id)))) ORDER BY user_id DESC
+ user_id 
+---------
+       5
+       4
+       3
+       2
+       1
+(5 rows)
+
+-- unions and ctes inside subqueries in where clause with a not pushdownable correlated subquery
+-- should error out
+SELECT 
+	DISTINCT user_id 
+FROM 
+	events_table 
+WHERE 
+	event_type IN 
+(
+	SELECT
+		users_table.user_id
+	FROM
+		(
+			(WITH cte_1 AS (SELECT user_id FROM users_table) SELECT * FROM cte_1) UNION 
+			(WITH cte_1 AS (SELECT user_id FROM users_table) SELECT * FROM cte_1)
+		) as foo,
+		users_table
+		WHERE users_table.value_2 = foo.user_id  AND events_table.user_id = users_table.user_id
+		LIMIT 5
+)
+ORDER BY 1 DESC;
+DEBUG:  generating subplan 76_1 for CTE cte_1: SELECT user_id FROM public.users_table
+DEBUG:  generating subplan 76_2 for CTE cte_1: SELECT user_id FROM public.users_table
+DEBUG:  generating subplan 76_3 for subquery SELECT cte_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('76_1'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_1 UNION SELECT cte_1.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('76_2'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) cte_1
+DEBUG:  Plan 76 query after replacing subqueries and CTEs: SELECT DISTINCT user_id FROM public.events_table WHERE (event_type IN (SELECT users_table.user_id FROM (SELECT intermediate_result.user_id FROM read_intermediate_result('76_3'::text, 'binary'::citus_copy_format) intermediate_result(user_id integer)) foo, public.users_table WHERE ((users_table.value_2 = foo.user_id) AND (events_table.user_id = users_table.user_id)) LIMIT 5)) ORDER BY user_id DESC
+ERROR:  cannot push down this subquery
+DETAIL:  Limit in subquery is currently unsupported when a subquery references a column from another query
+SET client_min_messages TO DEFAULT;
+SET search_path TO public;

src/test/regress/multi_schedule

@@ -42,7 +42,7 @@ test: multi_partitioning_utils multi_partitioning
 # ----------
 # Tests for recursive subquery planning
 # ----------
-test: subquery_basics subquery_local_tables subquery_executors subquery_and_cte
+test: subquery_basics subquery_local_tables subquery_executors subquery_and_cte set_operations set_operation_and_local_tables
 test: subqueries_deep subquery_view subquery_partitioning subquery_complex_target_list subqueries_not_supported  
 test: subquery_prepared_statements
 
@@ -95,7 +95,8 @@ test: multi_large_table_join_planning multi_large_table_pruning multi_large_tabl
 # Tests for recursive planning.
 # ---------
 
-test: with_nested with_where with_basics with_prepare with_modifying with_executors with_join with_partitioning
+test: with_nested with_where with_basics with_prepare with_set_operations
+test: with_modifying with_executors with_join with_partitioning
 
 # ----------
 # Tests to check our large record loading and shard deletion behavior

src/test/regress/sql/multi_insert_select.sql

@@ -538,11 +538,14 @@ FROM
 
 ROLLBACK;
 
--- We do not support any set operations
+-- We do support set operations through recursive planning
+BEGIN;
+SET LOCAL client_min_messages TO DEBUG;
 INSERT INTO
   raw_events_first(user_id)
   (SELECT user_id FROM raw_events_first) INTERSECT
   (SELECT user_id FROM raw_events_first);
+ROLLBACK;
 
 -- If the query is router plannable then it is executed via the coordinator
 INSERT INTO

src/test/regress/sql/multi_mx_router_planner.sql

@@ -353,15 +353,12 @@ SELECT * FROM (
 ) AS combination
 ORDER BY 1;
 
--- union queries are not supported if not router plannable
+-- union queries are supported through recursive planning
--- there is an inconsistency on shard pruning between
+SET client_min_messages TO DEBUG1;
--- ubuntu/mac disabling log messages for this queries only
-
-SET client_min_messages to 'NOTICE';
-
 (SELECT * FROM articles_hash_mx WHERE author_id = 1)
 UNION
-(SELECT * FROM articles_hash_mx WHERE author_id = 2);
+(SELECT * FROM articles_hash_mx WHERE author_id = 2)
+ORDER BY 1,2;
 
 
 SELECT * FROM (

src/test/regress/sql/multi_router_planner.sql

@@ -422,15 +422,18 @@ SELECT * FROM (
 ) AS combination
 ORDER BY 1;
 
--- top-level union queries are not supported if not router plannable
+-- top-level union queries are supported through recursive planning
--- there is an inconsistency on shard pruning between
--- ubuntu/mac disabling log messages for this queries only
 
 SET client_min_messages to 'NOTICE';
 
-(SELECT * FROM articles_hash WHERE author_id = 1)
+(
+  (SELECT * FROM articles_hash WHERE author_id = 1)
+  UNION
+  (SELECT * FROM articles_hash WHERE author_id = 3)
+)
 UNION
-(SELECT * FROM articles_hash WHERE author_id = 2);
+(SELECT * FROM articles_hash WHERE author_id = 2)
+ORDER BY 1,2,3;
 
 -- unions in subqueries are supported with subquery pushdown
 SELECT * FROM (

src/test/regress/sql/multi_simple_queries.sql

@@ -116,9 +116,10 @@ SELECT author_id, sum(word_count) AS corpus_size FROM articles
 	HAVING sum(word_count) > 40000
 	ORDER BY sum(word_count) DESC;
 
--- UNION/INTERSECT queries are unsupported if on multiple shards
+-- UNION/INTERSECT queries are supported if on multiple shards
 SELECT * FROM articles WHERE author_id = 10 UNION
-SELECT * FROM articles WHERE author_id = 2; 
+SELECT * FROM articles WHERE author_id = 2
+ORDER BY 1,2,3;
 
 -- queries using CTEs are supported
 WITH long_names AS ( SELECT id FROM authors WHERE char_length(name) > 15 )

src/test/regress/sql/multi_subquery.sql

@@ -4,7 +4,6 @@
 -- no need to set shardid sequence given that we're not creating any shards
 
 SET citus.next_shard_id TO 570032;
-SET citus.enable_router_execution TO FALSE;
 
 -- Check that we error out if shard min/max values are not exactly same.
 SELECT
@@ -74,7 +73,9 @@ SELECT count(*) FROM (
    SELECT l_orderkey FROM lineitem_subquery JOIN (SELECT random()::int r) sub ON (l_orderkey = r) WHERE r > 10
 ) b;
 
--- Check that we error out if there is non relation subqueries
+SET client_min_messages TO DEBUG;
+
+-- If there is non relation subqueries then we recursively plan
 SELECT count(*) FROM
 (
    (SELECT l_orderkey FROM lineitem_subquery) UNION ALL
@@ -82,21 +83,23 @@ SELECT count(*) FROM
 ) b;
 
 
--- Check that we error out if queries in union do not include partition columns.
+-- If queries in union do not include partition columns then we recursively plan
-
 SELECT count(*) FROM
 (
    (SELECT l_orderkey FROM lineitem_subquery) UNION
    (SELECT l_partkey FROM lineitem_subquery)
 ) b;
 
--- Check that we run union queries if partition column is selected.
+-- Check that we push down union queries if partition column is selected (no DEBUG messages)
 
 SELECT count(*) FROM
 (
    (SELECT l_orderkey FROM lineitem_subquery) UNION
    (SELECT l_orderkey FROM lineitem_subquery)
 ) b;
+
+RESET client_min_messages;
+
 -- we'd error out if inner query has Limit but subquery_pushdown is not set
 -- but we recursively plan the query
 SELECT
@@ -516,6 +519,8 @@ CREATE TABLE subquery_pruning_varchar_test_table
 SELECT master_create_distributed_table('subquery_pruning_varchar_test_table', 'a', 'hash');
 SELECT master_create_worker_shards('subquery_pruning_varchar_test_table', 4, 1);
 
+-- temporarily disable router executor to test pruning behaviour of subquery pushdown
+SET citus.enable_router_execution TO off;
 SET client_min_messages TO DEBUG2;
 
 SELECT * FROM
@@ -560,6 +565,8 @@ AS foo;
 
 DROP TABLE subquery_pruning_varchar_test_table;
 
+RESET citus.enable_router_execution;
+
 -- Simple join subquery pushdown
 SELECT
 	avg(array_length(events, 1)) AS event_average
@@ -793,4 +800,3 @@ DROP FUNCTION run_command_on_master_and_workers(p_sql text);
 SET client_min_messages TO DEFAULT;
 
 SET citus.subquery_pushdown to OFF;
-SET citus.enable_router_execution TO 'true';

src/test/regress/sql/multi_subquery_complex_queries.sql

@@ -8,8 +8,6 @@
 -- SET citus.next_shard_id TO 1400000;
 ALTER SEQUENCE pg_catalog.pg_dist_jobid_seq RESTART 1400000;
  
-SET citus.enable_router_execution TO FALSE;
-
  -- 
  -- UNIONs and JOINs mixed
  --
@@ -132,7 +130,7 @@ GROUP BY
 ORDER BY 
   types;
 
--- not supported since events_subquery_2 doesn't have partition key on the target list
+-- supported through recursive planning since events_subquery_2 doesn't have partition key on the target list
 -- within the shuffled target list
 SELECT ("final_query"."event_types") as types, count(*) AS sumOfEventType
 FROM
@@ -191,7 +189,7 @@ GROUP BY
 ORDER BY 
   types;
 
--- not supported since events_subquery_2 doesn't have partition key on the target list
+-- supported through recursive planning since events_subquery_2 doesn't have partition key on the target list
 SELECT ("final_query"."event_types") as types, count(*) AS sumOfEventType
 FROM
   ( SELECT *, random()
@@ -711,7 +709,7 @@ ON (t.user_id = q.user_id)) as final_query
 GROUP BY types
 ORDER BY types;
 
--- not supported since subquery 3 does not have partition key
+-- supported through recursive planning since subquery 3 does not have partition key
 SELECT ("final_query"."event_types") as types, count(*) AS sumOfEventType
 FROM
   ( SELECT *, random()
@@ -763,7 +761,7 @@ INNER JOIN
 GROUP BY types
 ORDER BY types;
 
--- not supported since events_subquery_4 does not have partition key on the 
+-- supported through recursive planning since events_subquery_4 does not have partition key on the 
 -- target list
 SELECT ("final_query"."event_types") as types, count(*) AS sumOfEventType
 FROM
@@ -2105,10 +2103,10 @@ GROUP BY
 ORDER BY 
   types;
 
--- not supported due to offset
+-- supported through recursive planning
 SELECT ("final_query"."event_types") as types, count(*) AS sumOfEventType
 FROM
-  ( SELECT *, random()
+  ( SELECT *
    FROM
      ( SELECT "t"."user_id", "t"."time", unnest("t"."collected_events") AS "event_types"
       FROM
@@ -2152,7 +2150,7 @@ FROM
                      FROM 
                       events_table as "events"
                      WHERE 
-                      event_type IN (4, 5)) events_subquery_4) OFFSET 3) t1
+                      event_type IN (4, 5)) events_subquery_4) ORDER BY 1, 2 OFFSET 3) t1
          GROUP BY "t1"."user_id") AS t) "q" 
 INNER JOIN
      (SELECT 
@@ -2273,11 +2271,9 @@ FROM
                     ) events_subquery_4)) t1
          GROUP BY "t1"."user_id") AS t) "q" 
 INNER JOIN
-     (SELECT random()::int as user_id) AS t 
+     (SELECT 1 as user_id) AS t 
     ON (t.user_id = q.user_id)) as final_query
 GROUP BY 
   types
 ORDER BY 
   types;
-
-SET citus.enable_router_execution TO TRUE;

src/test/regress/sql/multi_subquery_complex_reference_clause.sql

@@ -8,8 +8,6 @@
 -- SET citus.next_shard_id TO 1400000;
 ALTER SEQUENCE pg_catalog.pg_dist_jobid_seq RESTART 1400000;
 
-SET citus.enable_router_execution TO FALSE;
-
 CREATE TABLE user_buy_test_table(user_id int, item_id int, buy_count int);
 SELECT create_distributed_table('user_buy_test_table', 'user_id');
 INSERT INTO user_buy_test_table VALUES(1,2,1);
@@ -161,22 +159,27 @@ SELECT count(*) FROM
 SELECT count(*) FROM user_buy_test_table RIGHT JOIN (SELECT * FROM generate_series(1,10) id) users_ref_test_table
 ON user_buy_test_table.item_id = users_ref_test_table.id;
 
--- volatile functions cannot be used as table expressions
+-- volatile functions can be used as table expressions through recursive planning
+SET client_min_messages TO DEBUG;
+
 SELECT count(*) FROM
   (SELECT random() FROM user_buy_test_table JOIN random() AS users_ref_test_table(id)
   ON user_buy_test_table.item_id > users_ref_test_table.id) subquery_1;
 
--- cannot sneak in a volatile function as a parameter
+-- can sneak in a volatile function as a parameter
 SELECT count(*) FROM
-  (SELECT random() FROM user_buy_test_table JOIN generate_series(random()::int,10) AS users_ref_test_table(id)
+  (SELECT item_id FROM user_buy_test_table JOIN generate_series(random()::int,10) AS users_ref_test_table(id)
-  ON user_buy_test_table.item_id > users_ref_test_table.id) subquery_1;
+  ON user_buy_test_table.item_id > users_ref_test_table.id) subquery_1
+WHERE item_id = 6;
 
--- cannot perform a union with table function
+-- can perform a union with table function through recursive planning
 SELECT count(*) FROM
   (SELECT user_id FROM user_buy_test_table
    UNION ALL
    SELECT id FROM generate_series(1,10) AS users_ref_test_table(id)) subquery_1;
 
+RESET client_min_messages;
+
 -- subquery without FROM can be the inner relationship in a join
 SELECT count(*) FROM
   (SELECT random() FROM user_buy_test_table JOIN (SELECT 4 AS id) users_ref_test_table
@@ -194,7 +197,7 @@ ON user_buy_test_table.item_id = users_ref_test_table.id;
 SELECT count(*) FROM user_buy_test_table RIGHT JOIN (SELECT 5 AS id) users_ref_test_table
 ON user_buy_test_table.item_id = users_ref_test_table.id;
 
--- cannot perform a union with subquery without FROM
+-- can perform a union with subquery without FROM
 SELECT count(*) FROM
   (SELECT user_id FROM user_buy_test_table
    UNION ALL
@@ -770,9 +773,10 @@ INNER JOIN
         value_1 > 2 and value_1 < 4) AS t
     ON (t.user_id = q.user_id)) as final_query
 ORDER BY
-  types;
+  types
+LIMIT 5;
 
-  -- reference table exist in the subquery of union, should error out
+  -- reference table exist in the subquery of union
 SELECT ("final_query"."event_types") as types, count(*) AS sumOfEventType
 FROM
   ( SELECT
@@ -981,15 +985,16 @@ SELECT foo.user_id FROM
 ) as foo;
 
 -- not pushdownable since group by is on the reference table column
--- recursively planned, but hits unsupported clause type error on the top level query
+-- recursively planned
 SELECT foo.user_id FROM
 (
   SELECT r.user_id, random() FROM users_table m JOIN events_reference_table r ON int4eq(m.user_id, r.user_id)
   GROUP BY r.user_id
-) as foo;
+) as foo
+ORDER BY 1 DESC;
 
 -- not pushdownable since the group by contains at least one distributed table
--- recursively planned, but hits unsupported clause type error on the top level query
+-- recursively planned
 SELECT foo.user_id FROM
 (
   SELECT r.user_id, random() FROM users_table m JOIN events_reference_table r ON int4eq(m.user_id, r.user_id)
@@ -998,13 +1003,16 @@ SELECT foo.user_id FROM
 ORDER BY 1 LIMIT 3;
 
 -- not pushdownable since distinct is on the reference table column
--- recursively planned, but hits unsupported clause type error on the top level query
+-- recursively planned
 SELECT foo.user_id FROM
 (
   SELECT DISTINCT r.user_id, random() FROM users_table m JOIN events_reference_table r ON int4eq(m.user_id, r.user_id)
-) as foo;
+) as foo
+ORDER BY 1 DESC
+LIMIT 5;
 
 -- not supported since distinct on is on the reference table column
+-- but recursively planned
 SELECT foo.user_id FROM
 (
   SELECT DISTINCT ON(r.user_id) r.user_id, random() FROM users_table m JOIN events_reference_table r ON int4eq(m.user_id, r.user_id)
@@ -1069,7 +1077,8 @@ SELECT * FROM
 SELECT * FROM
 (
   SELECT DISTINCT users_reference_table.user_id FROM users_reference_table, (SELECT user_id, random() FROM events_table) as us_events WHERE users_reference_table.user_id = us_events.user_id
-) as foo;
+) as foo
+ORDER BY 1;
 
 -- the following query is safe to push down since the DISTINCT clause include distribution column
 SELECT * FROM

src/test/regress/sql/multi_subquery_union.sql

@@ -6,7 +6,6 @@
 -- We don't need shard id sequence here, so commented out to prevent conflicts with concurrent tests
 -- SET citus.next_shard_id TO 1400000;
 
-SET citus.enable_router_execution TO false;
 -- a very simple union query
 SELECT user_id, counter
 FROM (
@@ -568,18 +567,17 @@ LIMIT 5;
 
 -- now lets also have some unsupported queries
 
--- group by is not on the partition key
+-- group by is not on the partition key, supported through recursive planning
--- but we can still recursively plan it, though that is not suffient for pushdown
--- of the whole query
 SELECT user_id, sum(counter) 
 FROM (
     SELECT user_id, sum(value_2) AS counter FROM events_table GROUP BY user_id
       UNION
     SELECT value_1 as user_id, sum(value_2) AS counter FROM users_table GROUP BY value_1
 ) user_id 
-GROUP BY user_id;
+GROUP BY user_id
+ORDER BY 1,2;
 
--- partition key is not selected
+-- partition key is not selected, supported through recursive planning
 SELECT sum(counter) 
 FROM (
     SELECT user_id, sum(value_2) AS counter FROM users_table where value_1 < 1 GROUP BY user_id HAVING sum(value_2) > 25
@@ -594,7 +592,7 @@ FROM (
 ) user_id 
 GROUP BY user_id ORDER BY 1 DESC LIMIT 5;
 
--- excepts within unions are not supported
+-- excepts within unions are supported through recursive planning
 SELECT * FROM
 (
 (
@@ -615,7 +613,8 @@ UNION
       SELECT user_id, sum(value_2) AS counter FROM events_table GROUP BY user_id
 ) user_id_2
   GROUP BY user_id)
-) as ftop;
+) as ftop
+ORDER BY 1,2;
 
 -- non-equi join are not supported since there is no equivalence between the partition column
 SELECT user_id, sum(counter) 
@@ -719,9 +718,10 @@ SELECT user_id, sum(counter)
 FROM (
     SELECT user_id, sum(value_2) AS counter FROM events_table GROUP BY user_id
       UNION
-    SELECT user_id, sum(value_2) AS counter FROM users_table GROUP BY user_id OFFSET 4
+    SELECT user_id, sum(value_2) AS counter FROM users_table GROUP BY user_id ORDER BY user_id OFFSET 4
 ) user_id 
-GROUP BY user_id;
+GROUP BY user_id
+ORDER BY 1,2;
 
 -- lower level union does not return partition key with the other relations
 SELECT *
@@ -762,7 +762,8 @@ FROM (
             GROUP BY 
               user_id) user_id_2
          GROUP BY 
-            user_id)) AS ftop;
+            user_id)) AS ftop
+ORDER BY 1,2;
 
 
 -- some UNION all queries that are going to be pulled up
@@ -795,7 +796,7 @@ FROM
 ORDER BY 1 DESC, 2 DESC
 LIMIT 5;
 
--- we don't allow joins within unions
+-- we allow joins within unions
 SELECT 
   count(*)
 FROM 
@@ -805,9 +806,7 @@ FROM
   (SELECT users_table.user_id FROM events_table, users_table WHERE events_table.user_id = users_table.user_id)
 ) b;
 
--- we don't support pushing down subqueries without relations
+-- we support unions on subqueries without relations through recursive planning
--- recursive planning can replace that query, though the whole
--- query is not safe to pushdown
 SELECT 
   count(*)
 FROM 
@@ -817,11 +816,9 @@ FROM
   (SELECT 1)
 ) b;
 
--- we don't support pushing down subqueries without relations
+-- we support pushing down subqueries without relations through recursive planning
--- recursive planning can replace that query, though the whole
--- query is not safe to pushdown
 SELECT 
-  *
+  count(*)
 FROM 
 (
   (SELECT user_id FROM users_table)
@@ -829,7 +826,7 @@ FROM
   (SELECT (random() * 100)::int)
 ) b;
 
--- we don't support subqueries without relations
+-- we support subqueries without relations within a union
 SELECT 
   user_id, value_3
 FROM 
@@ -849,9 +846,7 @@ FROM
 ORDER BY 1 DESC, 2 DESC
 LIMIT 5;
 
--- we don't support pushing down subqueries without relations
+-- we support pushing down subqueries without relations through recursive planning
--- recursive planning can replace that query, though the whole
--- query is not safe to pushdown
 SELECT ("final_query"."event_types") as types, count(*) AS sumOfEventType
 FROM
   ( SELECT *, random()
@@ -895,7 +890,5 @@ FROM
 GROUP BY types
 ORDER BY types;
 
-SET citus.enable_router_execution TO true;
-
 DROP TABLE events_reference_table;
 DROP TABLE users_reference_table;

src/test/regress/sql/multi_view.sql

@@ -283,10 +283,11 @@ SELECT et.user_id, et.time FROM events_table et WHERE et.user_id IN (SELECT user
 -- it is supported when it is a router query
 SELECT count(*) FROM events_table et WHERE et.user_id IN (SELECT user_id FROM recent_selected_users WHERE user_id = 1);
 
--- expected this to work but it did not
+-- union between views is supported through recursive planning
 (SELECT user_id FROM recent_users) 
 UNION
-(SELECT user_id FROM selected_users);
+(SELECT user_id FROM selected_users)
+ORDER BY 1;
 
 -- wrapping it inside a SELECT * works
 SELECT *
@@ -313,7 +314,7 @@ SELECT count(*)
 		(SELECT user_id FROM selected_users) ) u
 	WHERE user_id < 2 AND user_id > 0;
 
--- expected this to work but it does not
+-- UNION ALL between views is supported through recursive planning
 SELECT count(*)
 	FROM (
 		(SELECT user_id FROM recent_users) 

src/test/regress/sql/set_operation_and_local_tables.sql

@@ -0,0 +1,102 @@
+CREATE SCHEMA recursive_set_local;
+SET search_path TO recursive_set_local, public;
+
+CREATE TABLE recursive_set_local.test (x int, y int);
+SELECT create_distributed_table('test', 'x');
+
+CREATE TABLE recursive_set_local.ref (a int, b int);
+SELECT create_reference_table('ref');
+
+CREATE TABLE recursive_set_local.local_test (x int, y int);
+
+INSERT INTO test VALUES (1,1), (2,2);
+INSERT INTO ref VALUES (2,2), (3,3);
+INSERT INTO local_test VALUES (3,3), (4,4);
+
+SET client_min_messages TO DEBUG;
+
+-- we should be able to run set operations with local tables
+(SELECT x FROM test) INTERSECT (SELECT x FROM local_test) ORDER BY 1 DESC;
+
+-- we should be able to run set operations with generate series
+(SELECT x FROM test) INTERSECT (SELECT i FROM generate_series(0, 100) i) ORDER BY 1 DESC;
+
+-- we'd first recursively plan the query with "test", thus don't need to recursively 
+-- plan other query
+(SELECT x FROM test LIMIT 5) INTERSECT (SELECT i FROM generate_series(0, 100) i) ORDER BY 1 DESC;
+
+-- this doesn't require any recursive planning
+(SELECT a FROM ref) INTERSECT (SELECT i FROM generate_series(0, 100) i) ORDER BY 1 DESC;
+
+-- same query with a failure on the worker (i.e., division by zero)
+(SELECT x FROM test) INTERSECT (SELECT i/0 FROM generate_series(0, 100) i) ORDER BY 1 DESC;
+
+-- we should be able to run set operations with generate series and local tables as well
+((SELECT x FROM local_test) UNION ALL (SELECT x FROM test)) INTERSECT (SELECT i FROM generate_series(0, 100) i) ORDER BY 1 DESC;
+
+-- two local tables are on different leaf queries, so safe to plan & execute
+((SELECT x FROM local_test) UNION ALL (SELECT x FROM test)) INTERSECT (SELECT x FROM local_test) ORDER BY 1 DESC;
+
+-- use ctes inside unions along with local tables on the top level
+WITH 
+cte_1 AS (SELECT user_id FROM users_table),
+cte_2 AS (SELECT user_id FROM events_table)
+((SELECT * FROM cte_1) UNION (SELECT * FROM cte_2) UNION (SELECT x FROM local_test)) INTERSECT (SELECT i FROM generate_series(0, 100) i)
+ORDER BY 1 DESC;
+
+-- CTEs inside subqueries unioned with local table
+-- final query is real-time
+SELECT
+	count(*)
+FROM
+	(
+		((WITH cte_1 AS (SELECT x FROM test) SELECT * FROM cte_1) UNION 
+		(WITH cte_1 AS (SELECT a FROM ref) SELECT * FROM cte_1)) INTERSECT
+		(SELECT x FROM local_test)
+	) as foo,
+	test
+	WHERE test.y = foo.x;
+
+-- CTEs inside subqueries unioned with local table
+-- final query is router
+SELECT
+	count(*)
+FROM
+	(
+		((WITH cte_1 AS (SELECT x FROM test) SELECT * FROM cte_1) UNION 
+		(WITH cte_1 AS (SELECT a FROM ref) SELECT * FROM cte_1)) INTERSECT
+		(SELECT x FROM local_test)
+	) as foo,
+	ref
+	WHERE ref.a = foo.x;
+
+-- subquery union in WHERE clause without parition column equality is recursively planned including the local tables
+SELECT * FROM test a WHERE x IN (SELECT x FROM test b UNION SELECT y FROM test c UNION SELECT y FROM local_test d) ORDER BY 1,2;
+
+-- same query with subquery in where is wrapped in CTE
+SELECT * FROM test a WHERE x IN (WITH cte AS (SELECT x FROM test b UNION SELECT y FROM test c UNION SELECT y FROM local_test d) SELECT * FROM cte) ORDER BY 1,2;
+
+-- not supported since local table is joined with a set operation
+SELECT * FROM ((SELECT * FROM test) EXCEPT (SELECT * FROM test ORDER BY x LIMIT 1)) u JOIN local_test USING (x) ORDER BY 1,2;
+
+-- though we replace some queries including the local query, the intermediate result is on the outer part of an outer join 
+SELECT * FROM ((SELECT * FROM local_test) INTERSECT (SELECT * FROM test ORDER BY x LIMIT 1)) u LEFT JOIN test USING (x) ORDER BY 1,2;
+
+-- we replace some queries including the local query, the intermediate result is on the inner part of an outer join 
+SELECT * FROM ((SELECT * FROM local_test) INTERSECT (SELECT * FROM test ORDER BY x LIMIT 1)) u RIGHT JOIN test USING (x) ORDER BY 1,2;
+
+-- recurively plan left part of the join, and run a final real-time query
+SELECT * FROM ((SELECT * FROM local_test) INTERSECT (SELECT * FROM test ORDER BY x LIMIT 1)) u INNER JOIN test USING (x) ORDER BY 1,2;
+
+-- distributed table in WHERE clause, but not FROM clause still disallowed
+SELECT * FROM ((SELECT x FROM test) UNION (SELECT x FROM (SELECT x FROM local_test) as foo WHERE x IN (SELECT x FROM test))) u ORDER BY 1;
+
+SET citus.enable_repartition_joins TO ON;
+
+--  repartition is recursively planned before the set operation
+(SELECT x FROM test) INTERSECT (SELECT t1.x FROM test as t1, test as t2 WHERE t1.x = t2.y LIMIT 2) INTERSECT (((SELECT x FROM local_test) UNION ALL (SELECT x FROM test)) INTERSECT (SELECT i FROM generate_series(0, 100) i)) ORDER BY 1 DESC; 
+
+SET citus.enable_repartition_joins TO OFF;
+
+RESET client_min_messages;
+DROP SCHEMA recursive_set_local CASCADE;

src/test/regress/sql/set_operations.sql

@@ -0,0 +1,173 @@
+CREATE SCHEMA recursive_union;
+SET search_path TO recursive_union, public;
+
+CREATE TABLE recursive_union.test (x int, y int);
+SELECT create_distributed_table('test', 'x');
+
+CREATE TABLE recursive_union.ref (a int, b int);
+SELECT create_reference_table('ref');
+
+INSERT INTO test VALUES (1,1), (2,2);
+INSERT INTO ref VALUES (2,2), (3,3);
+
+-- top-level set operations are supported through recursive planning
+SET client_min_messages TO DEBUG;
+
+(SELECT * FROM test) UNION (SELECT * FROM test) ORDER BY 1,2;
+(SELECT * FROM test) UNION (SELECT * FROM ref) ORDER BY 1,2;
+(SELECT * FROM ref) UNION (SELECT * FROM ref) ORDER BY 1,2;
+
+(SELECT * FROM test) UNION ALL (SELECT * FROM test) ORDER BY 1,2;
+(SELECT * FROM test) UNION ALL (SELECT * FROM ref) ORDER BY 1,2;
+(SELECT * FROM ref) UNION ALL (SELECT * FROM ref) ORDER BY 1,2;
+
+(SELECT * FROM test) INTERSECT (SELECT * FROM test) ORDER BY 1,2;
+(SELECT * FROM test) INTERSECT (SELECT * FROM ref) ORDER BY 1,2;
+(SELECT * FROM ref) INTERSECT (SELECT * FROM ref) ORDER BY 1,2;
+
+(SELECT * FROM test) INTERSECT ALL (SELECT * FROM test) ORDER BY 1,2;
+(SELECT * FROM test) INTERSECT ALL (SELECT * FROM ref) ORDER BY 1,2;
+(SELECT * FROM ref) INTERSECT ALL (SELECT * FROM ref) ORDER BY 1,2;
+
+(SELECT * FROM test) EXCEPT (SELECT * FROM test) ORDER BY 1,2;
+(SELECT * FROM test) EXCEPT (SELECT * FROM ref) ORDER BY 1,2;
+(SELECT * FROM ref) EXCEPT (SELECT * FROM ref) ORDER BY 1,2;
+
+(SELECT * FROM test) EXCEPT ALL (SELECT * FROM test) ORDER BY 1,2;
+(SELECT * FROM test) EXCEPT ALL (SELECT * FROM ref) ORDER BY 1,2;
+(SELECT * FROM ref) EXCEPT ALL (SELECT * FROM ref) ORDER BY 1,2;
+
+-- more complex set operation trees are supported
+(SELECT * FROM test)
+INTERSECT
+(SELECT * FROM ref)
+UNION ALL
+(SELECT s, s FROM generate_series(1,10) s)
+EXCEPT
+(SELECT 1,1)
+UNION
+(SELECT test.x, ref.a FROM test LEFT JOIN ref ON (x = a))
+ORDER BY 1,2;
+
+-- within a subquery, some unions can be pushed down
+SELECT * FROM ((SELECT * FROM test) UNION (SELECT * FROM test)) u ORDER BY 1,2;
+SELECT * FROM ((SELECT x, y FROM test) UNION (SELECT y, x FROM test)) u ORDER BY 1,2;
+SELECT * FROM ((SELECT * FROM test) UNION (SELECT * FROM ref)) u ORDER BY 1,2;
+SELECT * FROM ((SELECT * FROM ref) UNION (SELECT * FROM ref)) u ORDER BY 1,2;
+
+SELECT * FROM ((SELECT * FROM test) UNION ALL (SELECT * FROM test)) u ORDER BY 1,2;
+SELECT * FROM ((SELECT x, y FROM test) UNION ALL (SELECT y, x FROM test)) u ORDER BY 1,2;
+SELECT * FROM ((SELECT * FROM test) UNION ALL (SELECT * FROM ref)) u ORDER BY 1,2;
+SELECT * FROM ((SELECT * FROM ref) UNION ALL (SELECT * FROM ref)) u ORDER BY 1,2;
+
+SELECT * FROM ((SELECT * FROM test) INTERSECT (SELECT * FROM test)) u ORDER BY 1,2;
+SELECT * FROM ((SELECT x, y FROM test) INTERSECT (SELECT y, x FROM test)) u ORDER BY 1,2;
+SELECT * FROM ((SELECT * FROM test) INTERSECT (SELECT * FROM ref)) u ORDER BY 1,2;
+SELECT * FROM ((SELECT * FROM ref) INTERSECT (SELECT * FROM ref)) u ORDER BY 1,2;
+
+SELECT * FROM ((SELECT * FROM test) EXCEPT (SELECT * FROM test)) u ORDER BY 1,2;
+SELECT * FROM ((SELECT x, y FROM test) EXCEPT (SELECT y, x FROM test)) u ORDER BY 1,2;
+SELECT * FROM ((SELECT * FROM test) EXCEPT (SELECT * FROM ref)) u ORDER BY 1,2;
+SELECT * FROM ((SELECT * FROM ref) EXCEPT (SELECT * FROM ref)) u ORDER BY 1,2;
+
+-- unions can even be pushed down within a join
+SELECT * FROM ((SELECT * FROM test) UNION (SELECT * FROM test)) u JOIN test USING (x) ORDER BY 1,2;
+SELECT * FROM ((SELECT * FROM test) UNION ALL (SELECT * FROM test)) u LEFT JOIN test USING (x) ORDER BY 1,2;
+
+-- unions cannot be pushed down if one leaf recurs
+SELECT * FROM ((SELECT * FROM test) UNION (SELECT * FROM test ORDER BY x LIMIT 1)) u JOIN test USING (x) ORDER BY 1,2;
+SELECT * FROM ((SELECT * FROM test) UNION ALL (SELECT * FROM test ORDER BY x LIMIT 1)) u LEFT JOIN test USING (x) ORDER BY 1,2;
+
+-- unions in a join without partition column equality (column names from first query are used for join)
+SELECT * FROM ((SELECT x, y FROM test) UNION (SELECT y, x FROM test)) u JOIN test USING (x) ORDER BY 1,2;
+SELECT * FROM ((SELECT x, y FROM test) UNION (SELECT 1, 1 FROM test)) u JOIN test USING (x) ORDER BY 1,2;
+
+-- a join between a set operation and a generate_series which is pushdownable
+ SELECT * FROM ((SELECT * FROM test) UNION (SELECT * FROM test ORDER BY x)) u JOIN generate_series(1,10) x USING (x) ORDER BY 1,2;
+
+-- a join between a set operation and a generate_series which is not pushdownable due to EXCEPT
+ SELECT * FROM ((SELECT * FROM test) EXCEPT (SELECT * FROM test ORDER BY x)) u JOIN generate_series(1,10) x USING (x) ORDER BY 1,2;
+
+-- subqueries in WHERE clause with set operations fails due to the current limitaions of recursive planning IN WHERE clause
+SELECT * FROM ((SELECT * FROM test) UNION (SELECT * FROM test)) foo WHERE x IN (SELECT y FROM test);
+
+-- subqueries in WHERE clause forced to be recursively planned
+SELECT * FROM ((SELECT * FROM test) UNION (SELECT * FROM test)) foo WHERE x IN (SELECT y FROM test ORDER BY 1 LIMIT 4) ORDER BY 1;
+
+-- now both the set operations and the sublink is recursively planned
+SELECT * FROM ((SELECT x,y FROM test) UNION (SELECT y,x FROM test)) foo WHERE x IN (SELECT y FROM test ORDER BY 1 LIMIT 4) ORDER BY 1;
+
+-- set operations are recursively planned and not the sublink, thus should error out
+SELECT * FROM ((SELECT x,y FROM test) UNION (SELECT y,x FROM test)) foo WHERE x IN (SELECT y FROM test) ORDER BY 1;
+
+-- set operations works fine with pushdownable window functions
+SELECT x, y, rnk FROM (SELECT *, rank() OVER my_win as rnk FROM test WINDOW my_win AS (PARTITION BY x ORDER BY y DESC)) as foo
+UNION
+SELECT x, y, rnk FROM (SELECT *, rank() OVER my_win as rnk FROM test WINDOW my_win AS (PARTITION BY x ORDER BY y DESC)) as bar
+ORDER BY 1 DESC, 2 DESC, 3 DESC;
+
+-- set operations errors out with non-pushdownable window functions
+SELECT x, y, rnk FROM (SELECT *, rank() OVER my_win as rnk FROM test WINDOW my_win AS (PARTITION BY y ORDER BY x DESC)) as foo
+UNION
+SELECT x, y, rnk FROM (SELECT *, rank() OVER my_win as rnk FROM test WINDOW my_win AS (PARTITION BY y ORDER BY x DESC)) as bar;
+
+-- other set operations in joins also cannot be pushed down
+SELECT * FROM ((SELECT * FROM test) EXCEPT (SELECT * FROM test ORDER BY x LIMIT 1)) u JOIN test USING (x) ORDER BY 1,2;
+SELECT * FROM ((SELECT * FROM test) INTERSECT (SELECT * FROM test ORDER BY x LIMIT 1)) u LEFT JOIN test USING (x) ORDER BY 1,2;
+
+-- distributed table in WHERE clause, but not FROM clause still disallowed
+SELECT * FROM ((SELECT * FROM test) UNION (SELECT * FROM ref WHERE a IN (SELECT x FROM test))) u ORDER BY 1,2;
+
+-- subquery union in WHERE clause with partition column equality and implicit join is pushed down
+SELECT * FROM test a WHERE x IN (SELECT x FROM test b WHERE y = 1 UNION SELECT x FROM test c WHERE y = 2) ORDER BY 1,2;
+
+-- subquery union in WHERE clause with partition column equality, without implicit join on partition column
+SELECT * FROM test a WHERE x NOT IN (SELECT x FROM test b WHERE y = 1 UNION SELECT x FROM test c WHERE y = 2) ORDER BY 1,2;
+
+-- subquery union in WHERE clause without parition column equality is recursively planned
+SELECT * FROM test a WHERE x IN (SELECT x FROM test b UNION SELECT y FROM test c) ORDER BY 1,2;
+
+-- correlated subquery with union in WHERE clause
+SELECT * FROM test a WHERE x IN (SELECT x FROM test b UNION SELECT y FROM test c WHERE a.x = c.x) ORDER BY 1,2;
+
+-- force unions to be planned while subqueries are being planned
+SELECT * FROM ((SELECT * FROM test) UNION (SELECT * FROM test) ORDER BY 1,2 LIMIT 5) as foo ORDER BY 1 DESC LIMIT 3;
+
+-- distinct and count distinct should work without any problems
+select count(DISTINCT t.x) FROM ((SELECT DISTINCT x FROM test) UNION (SELECT DISTINCT y FROM test)) as t(x) ORDER BY 1;
+select count(DISTINCT t.x) FROM ((SELECT count(DISTINCT x) FROM test) UNION (SELECT count(DISTINCT y) FROM test)) as t(x) ORDER BY 1;
+
+-- other agg. distincts are also supported when group by includes partition key 
+select avg(DISTINCT t.x) FROM ((SELECT avg(DISTINCT y) FROM test GROUP BY x) UNION (SELECT avg(DISTINCT y) FROM test GROUP BY x)) as t(x) ORDER BY 1;
+
+-- other agg. distincts are not supported when group by doesn't include partition key 
+select count(DISTINCT t.x) FROM ((SELECT avg(DISTINCT y) FROM test GROUP BY y) UNION (SELECT avg(DISTINCT y) FROM test GROUP BY y)) as t(x) ORDER BY 1;
+
+-- one of the leaves is a repartition join
+SET citus.enable_repartition_joins TO ON;
+
+--  repartition is recursively planned before the set operation
+(SELECT x FROM test) INTERSECT (SELECT t1.x FROM test as t1, test as t2 WHERE t1.x = t2.y LIMIT 0) ORDER BY 1 DESC; 
+
+--  repartition is recursively planned with the set operation
+(SELECT x FROM test) INTERSECT (SELECT t1.x FROM test as t1, test as t2 WHERE t1.x = t2.y) ORDER BY 1 DESC;
+
+SET citus.enable_repartition_joins TO OFF;
+
+-- this should be recursively planned
+CREATE VIEW set_view_recursive AS (SELECT y FROM test) UNION (SELECT y FROM test);
+SELECT * FROM set_view_recursive ORDER BY 1 DESC;
+
+-- this should be pushed down
+CREATE VIEW set_view_pushdown AS (SELECT x FROM test) UNION (SELECT x FROM test);
+SELECT * FROM set_view_pushdown ORDER BY 1 DESC;
+
+-- this should be recursively planned
+CREATE VIEW set_view_recursive_second AS SELECT u.x, test.y FROM ((SELECT x, y FROM test) UNION (SELECT 1, 1 FROM test)) u JOIN test USING (x) ORDER BY 1,2;
+SELECT * FROM set_view_recursive_second;
+
+-- this should create lots of recursive calls since both views and set operations lead to recursive plans :) 
+((SELECT x FROM set_view_recursive_second) INTERSECT (SELECT * FROM set_view_recursive)) EXCEPT (SELECT * FROM set_view_pushdown);
+
+RESET client_min_messages;
+DROP SCHEMA recursive_union CASCADE;

src/test/regress/sql/with_basics.sql

@@ -354,7 +354,7 @@ ORDER BY
 LIMIT
   5;
 
--- SELECT * FROM (SELECT * FROM cte UNION SELECT * FROM distributed_table) a; should error out
+-- SELECT * FROM (SELECT * FROM cte UNION SELECT * FROM distributed_table) a; should work
 WITH cte AS (
 	SELECT * FROM users_table
 )

src/test/regress/sql/with_set_operations.sql

@@ -0,0 +1,214 @@
+-- ===================================================================
+-- test recursive planning functionality with Set Operations and CTEs
+-- ===================================================================
+
+SET client_min_messages TO DEBUG1;
+
+-- use ctes inside unions on the top level
+WITH 
+cte_1 AS (SELECT user_id FROM users_table),
+cte_2 AS (SELECT user_id FROM events_table)
+(SELECT * FROM cte_1) UNION (SELECT * FROM cte_2)
+ORDER BY 1 DESC;
+
+
+-- use ctes inside unions in a subquery
+WITH 
+cte_1 AS (SELECT user_id FROM users_table),
+cte_2 AS (SELECT user_id FROM events_table)
+SELECT 
+	count(*) 
+FROM (
+		(SELECT * FROM cte_1) UNION (SELECT * FROM cte_2)
+	) as foo;
+
+
+-- cte with unions of other ctes
+WITH 
+cte_1 AS (SELECT user_id FROM users_table),
+cte_2 AS (SELECT user_id FROM events_table),
+cte_3 AS ((SELECT * FROM cte_1) UNION (SELECT * FROM cte_2))
+SELECT * FROM cte_3 ORDER BY 1 DESC;
+
+-- cte with unions of distributed table
+WITH 
+cte_1 AS ((SELECT user_id FROM users_table) UNION (SELECT user_id FROM users_table))
+SELECT * FROM cte_1 ORDER BY 1 DESC;
+
+-- cte with unions of tables is intersected with another query
+WITH 
+cte_1 AS ((SELECT user_id FROM users_table) UNION (SELECT user_id FROM users_table))
+(SELECT * FROM cte_1) INTERSECT (SELECT user_id FROM users_table) ORDER BY 1 DESC;
+
+-- cte with unions of tables is intersected with another query that involves except
+WITH 
+cte_1 AS ((SELECT user_id FROM users_table) UNION (SELECT user_id FROM users_table))
+(SELECT * FROM cte_1) 
+	INTERSECT 
+((SELECT user_id FROM events_table WHERE user_id < 3) EXCEPT (SELECT user_id FROM users_table WHERE user_id > 4)) ORDER BY 1 DESC;
+
+
+-- CTE inside a top level EXCEPT
+(WITH cte_1 AS (SELECT user_id FROM events_table WHERE user_id < 3) SELECT * FROM cte_1) INTERSECT (SELECT user_id FROM users_table) ORDER BY 1;   
+
+-- INTERSECT inside a CTE, which is inside a subquery
+SELECT 
+	DISTINCT users_table.user_id 
+FROM 
+	users_table, 
+	(WITH cte_1 AS (SELECT user_id FROM events_table WHERE user_id < 3 INTERSECT 
+					SELECT user_id FROM events_table WHERE user_id < 2) 
+	 SELECT * FROM cte_1) as foo
+WHERE
+	users_table.user_id = foo.user_id
+ORDER BY 1 DESC;
+
+-- UNION is created via outputs of CTEs, which is inside a subquery
+-- and the subquery is joined with a distributed table
+SELECT 
+	count(*) 
+FROM 
+	events_table,
+	(
+		WITH 
+		cte_1 AS (SELECT user_id FROM users_table),
+		cte_2 AS (SELECT user_id FROM events_table)
+		(SELECT * FROM cte_1) UNION (SELECT * FROM cte_2)
+	) as foo
+WHERE foo.user_id = events_table.event_type;
+
+-- joins inside unions that are safe to pushdown
+(SELECT DISTINCT events_table.user_id FROM users_table, events_table WHERE users_table.user_id = events_table.user_id )
+INTERSECT
+(SELECT DISTINCT events_table.user_id FROM users_table, events_table WHERE users_table.user_id = events_table.user_id )
+ORDER BY 1 DESC;
+
+-- joins inside unions that are not safe to pushdown
+(SELECT DISTINCT events_table.user_id FROM users_table, events_table WHERE users_table.user_id = events_table.user_id LIMIT 10)
+INTERSECT
+(SELECT DISTINCT events_table.user_id FROM users_table, events_table WHERE users_table.user_id = events_table.user_id LIMIT 10)
+ORDER BY 1 DESC;
+
+-- joins inside unions that are not safe to pushdown inside a subquery
+SELECT 
+	count(*) 
+FROM 
+	(SELECT DISTINCT value_2 FROM events_table) as events_table,
+	(WITH foo AS 
+		((SELECT DISTINCT events_table.user_id FROM users_table, events_table WHERE users_table.user_id = events_table.user_id )
+	 	INTERSECT
+		(SELECT DISTINCT events_table.user_id FROM users_table, events_table WHERE users_table.user_id = events_table.user_id LIMIT 10)) 
+	 SELECT * FROM foo) 
+	as foo
+WHERE 
+	foo.user_id = events_table.value_2;
+
+-- joins inside unions some safe to pushdown
+SELECT 
+	count(*) 
+FROM 
+	(WITH events_table AS (SELECT DISTINCT user_id FROM events_table) SELECT * FROM events_table) as events_table,
+	((SELECT DISTINCT events_table.user_id FROM users_table, events_table WHERE users_table.user_id = events_table.user_id )
+	INTERSECT
+	(SELECT DISTINCT events_table.user_id FROM users_table, events_table WHERE users_table.user_id = events_table.user_id LIMIT 10)) as foo
+WHERE 
+	foo.user_id = events_table.user_id;
+
+-- CTE inside unions
+(WITH cte_1 AS (SELECT user_id FROM users_table) SELECT * FROM cte_1) UNION 
+(WITH cte_1 AS (SELECT user_id FROM users_table) SELECT * FROM cte_1) ORDER BY 1 DESC; 
+
+-- more complex CTEs inside unions
+SELECT
+	count(*)
+FROM
+	(
+		(WITH cte_1 AS (SELECT user_id FROM users_table) SELECT * FROM cte_1) UNION 
+		(WITH cte_1 AS (SELECT user_id FROM users_table) SELECT * FROM cte_1)
+	) as foo,
+	users_table
+	WHERE users_table.value_2 = foo.user_id;
+
+-- CTEs with less alias than the input subquery
+(WITH cte_1(x) AS (SELECT user_id, value_2 FROM users_table) SELECT * FROM cte_1) UNION 
+(WITH cte_1(x) AS (SELECT user_id, value_2 FROM users_table) SELECT * FROM cte_1) ORDER BY 1 DESC, 2 DESC LIMIT 5;
+
+
+-- simple subqueries in WHERE with unions
+SELECT 
+	count(*)
+FROM
+	users_table
+WHERE
+	value_2 IN
+	(
+		WITH cte_1 AS
+		(
+			(SELECT user_id FROM users_table)
+			UNION
+		 	(SELECT user_id FROM events_table)
+		 ) SELECT DISTINCT user_id FROM cte_1
+)
+ORDER BY 1 DESC;
+
+-- simple subqueries in WHERE with unions and ctes
+SELECT 
+	count(*)
+FROM
+	users_table
+WHERE
+	value_2 IN
+	(
+		WITH 
+		cte_1 AS (SELECT user_id FROM users_table),
+		cte_2 AS (SELECT user_id FROM events_table)
+		(SELECT * FROM cte_1) UNION (SELECT * FROM cte_2)
+)
+ORDER BY 1 DESC;
+
+-- unions and ctes inside subqueries in where clause with a pushdownable correlated subquery
+SELECT 
+	DISTINCT user_id 
+FROM 
+	events_table 
+WHERE 
+	event_type IN 
+(
+	SELECT
+		users_table.user_id
+	FROM
+		(
+			(WITH cte_1 AS (SELECT user_id FROM users_table) SELECT * FROM cte_1) UNION 
+			(WITH cte_1 AS (SELECT user_id FROM users_table) SELECT * FROM cte_1)
+		) as foo,
+		users_table
+		WHERE users_table.value_2 = foo.user_id  AND events_table.user_id = users_table.user_id
+)
+ORDER BY 1 DESC;
+
+-- unions and ctes inside subqueries in where clause with a not pushdownable correlated subquery
+-- should error out
+SELECT 
+	DISTINCT user_id 
+FROM 
+	events_table 
+WHERE 
+	event_type IN 
+(
+	SELECT
+		users_table.user_id
+	FROM
+		(
+			(WITH cte_1 AS (SELECT user_id FROM users_table) SELECT * FROM cte_1) UNION 
+			(WITH cte_1 AS (SELECT user_id FROM users_table) SELECT * FROM cte_1)
+		) as foo,
+		users_table
+		WHERE users_table.value_2 = foo.user_id  AND events_table.user_id = users_table.user_id
+		LIMIT 5
+)
+ORDER BY 1 DESC;
+
+
+SET client_min_messages TO DEFAULT;
+
+SET search_path TO public;