Fix subquery reference to non-populated MV in CMV.

A subquery reference to a matview should be allowed by CREATE
MATERIALIZED VIEW WITH NO DATA, just like a direct reference is.

Per bug report from Laurent Sartran.

Backpatch to 9.3.

Author: kgrittn

src/backend/executor/execMain.c

@@ -864,7 +864,8 @@ InitPlan(QueryDesc *queryDesc, int eflags)
 		 * it is a parameterless subplan (not initplan), we suggest that it be
 		 * prepared to handle REWIND efficiently; otherwise there is no need.
 		 */
-		sp_eflags = eflags & EXEC_FLAG_EXPLAIN_ONLY;
+		sp_eflags = eflags
+			& (EXEC_FLAG_EXPLAIN_ONLY | EXEC_FLAG_WITH_NO_DATA);
 		if (bms_is_member(i, plannedstmt->rewindPlanIDs))
 			sp_eflags |= EXEC_FLAG_REWIND;
 

src/test/regress/expected/matview.out

@@ -385,3 +385,9 @@ SELECT * FROM hogeview WHERE i < 10;
 
 DROP TABLE hoge CASCADE;
 NOTICE:  drop cascades to materialized view hogeview
+-- allow subquery to reference unpopulated matview if WITH NO DATA is specified
+CREATE MATERIALIZED VIEW mv1 AS SELECT 1 AS col1 WITH NO DATA;
+CREATE MATERIALIZED VIEW mv2 AS SELECT * FROM mv1
+  WHERE col1 = (SELECT LEAST(col1) FROM mv1) WITH NO DATA;
+DROP MATERIALIZED VIEW mv1 CASCADE;
+NOTICE:  drop cascades to materialized view mv2

src/test/regress/sql/matview.sql

@@ -124,3 +124,9 @@ SELECT * FROM hogeview WHERE i < 10;
 VACUUM ANALYZE;
 SELECT * FROM hogeview WHERE i < 10;
 DROP TABLE hoge CASCADE;
+
+-- allow subquery to reference unpopulated matview if WITH NO DATA is specified
+CREATE MATERIALIZED VIEW mv1 AS SELECT 1 AS col1 WITH NO DATA;
+CREATE MATERIALIZED VIEW mv2 AS SELECT * FROM mv1
+  WHERE col1 = (SELECT LEAST(col1) FROM mv1) WITH NO DATA;
+DROP MATERIALIZED VIEW mv1 CASCADE;