Acquire appropriate locks when rewriting during RMV.

Since the query has not been freshly parsed when executing REFRESH
MATERIALIZED VIEW, locks must be explicitly taken before rewrite.

Backpatch to 9.3.

Andres Freund

Author: kgrittn

src/backend/commands/matview.c

@@ -242,9 +242,12 @@ refresh_matview_datafill(DestReceiver *dest, Query *query,
 	List	   *rewritten;
 	PlannedStmt *plan;
 	QueryDesc  *queryDesc;
+	Query	   *copied_query;
 
-	/* Rewrite, copying the given Query to make sure it's not changed */
-	rewritten = QueryRewrite((Query *) copyObject(query));
+	/* Lock and rewrite, using a copy to preserve the original query. */
+	copied_query = copyObject(query);
+	AcquireRewriteLocks(copied_query, false);
+	rewritten = QueryRewrite(copied_query);
 
 	/* SELECT should never rewrite to more or less than one SELECT query */
 	if (list_length(rewritten) != 1)