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.

src/backend/executor/execMain.c

@@ -865,7 +865,8 @@ 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

@@ -424,6 +424,12 @@ REFRESH MATERIALIZED VIEW mv;
 REFRESH MATERIALIZED VIEW CONCURRENTLY mv;
 DROP TABLE foo CASCADE;
 NOTICE:  drop cascades to materialized view mv
+-- 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
 -- make sure that types with unusual equality tests work
 CREATE TABLE boxes (id serial primary key, b box);
 INSERT INTO boxes (b) VALUES

src/test/regress/sql/matview.sql

@@ -155,6 +155,12 @@ REFRESH MATERIALIZED VIEW mv;
 REFRESH MATERIALIZED VIEW CONCURRENTLY mv;
 DROP TABLE foo 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;
+
 -- make sure that types with unusual equality tests work
 CREATE TABLE boxes (id serial primary key, b box);
 INSERT INTO boxes (b) VALUES