Merge pull request #1297 from citusdata/subquery_use_original_query

Subquery pushdown planner uses original query

src/backend/distributed/planner/multi_logical_planner.c

@@ -104,28 +104,35 @@ static MultiNode * ApplyCartesianProduct(MultiNode *leftNode, MultiNode *rightNo
  * Local functions forward declarations for subquery pushdown. Note that these
  * functions will be removed with upcoming subqery changes.
  */
-static MultiNode * SubqueryPushdownMultiPlanTree(Query *queryTree,
+static MultiNode * SubqueryPushdownMultiPlanTree(Query *queryTree);
-												 List *subqueryEntryList);
 static void ErrorIfSubqueryJoin(Query *queryTree);
 static MultiTable * MultiSubqueryPushdownTable(RangeTblEntry *subqueryRangeTableEntry);
 
 
 /*
- * MultiLogicalPlanCreate takes in a parsed query tree, uses helper functions to
+ * MultiLogicalPlanCreate takes in both the original query and its corresponding modified
- * create logical plan and adds a root node to top of it.
+ * query tree yield by the standard planner. It uses helper functions to create logical
+ * plan and adds a root node to top of it. The  original query is only used for subquery
+ * pushdown planning.
  */
 MultiTreeRoot *
-MultiLogicalPlanCreate(Query *queryTree)
+MultiLogicalPlanCreate(Query *originalQuery, Query *queryTree)
 {
 	MultiNode *multiQueryNode = NULL;
 	MultiTreeRoot *rootNode = NULL;
+	List *subqueryEntryList = NULL;
 
-	List *subqueryEntryList = SubqueryEntryList(queryTree);
+	/*
+	 * We check the existence of subqueries in the modified query given that
+	 * if postgres already flattened the subqueries, MultiPlanTree() can plan
+	 * corresponding distributed plan.
+	 */
+	subqueryEntryList = SubqueryEntryList(queryTree);
 	if (subqueryEntryList != NIL)
 	{
 		if (SubqueryPushdown)
 		{
-			multiQueryNode = SubqueryPushdownMultiPlanTree(queryTree, subqueryEntryList);
+			multiQueryNode = SubqueryPushdownMultiPlanTree(originalQuery);
 		}
 		else
 		{
@@ -1982,7 +1989,7 @@ ApplyCartesianProduct(MultiNode *leftNode, MultiNode *rightNode,
  * from other parts of code although it causes some code duplication.
  */
 static MultiNode *
-SubqueryPushdownMultiPlanTree(Query *queryTree, List *subqueryEntryList)
+SubqueryPushdownMultiPlanTree(Query *queryTree)
 {
 	List *targetEntryList = queryTree->targetList;
 	List *qualifierList = NIL;
@@ -1997,6 +2004,7 @@ SubqueryPushdownMultiPlanTree(Query *queryTree, List *subqueryEntryList)
 	MultiExtendedOp *extendedOpNode = NULL;
 	MultiNode *currentTopNode = NULL;
 	RangeTblEntry *subqueryRangeTableEntry = NULL;
+	List *subqueryEntryList = SubqueryEntryList(queryTree);
 
 	/* verify we can perform distributed planning on this query */
 	ErrorIfQueryNotSupported(queryTree);

src/backend/distributed/planner/multi_planner.c

@@ -295,7 +295,7 @@ CreateDistributedPlan(PlannedStmt *localPlan, Query *originalQuery, Query *query
 		if ((!distributedPlan || distributedPlan->planningError) && !hasUnresolvedParams)
 		{
 			/* Create and optimize logical plan */
-			MultiTreeRoot *logicalPlan = MultiLogicalPlanCreate(query);
+			MultiTreeRoot *logicalPlan = MultiLogicalPlanCreate(originalQuery, query);
 			MultiLogicalPlanOptimize(logicalPlan, plannerRestrictionContext);
 
 			/*

src/include/distributed/multi_logical_planner.h

@@ -180,7 +180,7 @@ extern bool SubqueryPushdown;
 
 
 /* Function declarations for building logical plans */
-extern MultiTreeRoot * MultiLogicalPlanCreate(Query *queryTree);
+extern MultiTreeRoot * MultiLogicalPlanCreate(Query *originalQuery, Query *queryTree);
 extern bool NeedsDistributedPlanning(Query *queryTree);
 extern MultiNode * ParentNode(MultiNode *multiNode);
 extern MultiNode * ChildNode(MultiUnaryNode *multiNode);

src/test/regress/output/multi_subquery.source

@@ -178,7 +178,8 @@ SELECT count(*) FROM
    (SELECT l_orderkey FROM lineitem_subquery) UNION ALL
    (SELECT 1::bigint)
 ) b;
-ERROR:  could not run distributed query with complex table expressions
+ERROR:  cannot push down this subquery
+DETAIL:  Union All clauses are currently unsupported
 ---
 -- TEMPORARLY DISABLE UNIONS WITHOUT JOINS
 ---

src/test/regress/output/multi_subquery_0.source

@@ -178,7 +178,8 @@ SELECT count(*) FROM
    (SELECT l_orderkey FROM lineitem_subquery) UNION ALL
    (SELECT 1::bigint)
 ) b;
-ERROR:  could not run distributed query with complex table expressions
+ERROR:  cannot push down this subquery
+DETAIL:  Union All clauses are currently unsupported
 ---
 -- TEMPORARLY DISABLE UNIONS WITHOUT JOINS
 ---