Fix mishandling of OLD/NEW references in subqueries in rule actions.

If a rule action contains a subquery that refers to columns from OLD
or NEW, then those are really lateral references, and the planner will
complain if it sees such things in a subquery that isn't marked as
lateral. However, at rule-definition time, the user isn't required to
mark the subquery with LATERAL, and so it can fail when the rule is
used.

Fix this by marking such subqueries as lateral in the rewriter, at the
point where they're used.

Dean Rasheed and Tom Lane, per report from Alexander Lakhin.
Back-patch to all supported branches.

Discussion: https://postgr.es/m/5e09da43-aaba-7ea7-0a51-a2eb981b058b%40gmail.com

1 files changed, 18 insertions, 4 deletions

diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
index b7277d99741..9103b35c774 100644
--- a/src/backend/rewrite/rewriteHandler.c
+++ b/src/backend/rewrite/rewriteHandler.c
@@ -348,6 +348,7 @@ rewriteRuleAction(Query *parsetree,
 	Query	   *sub_action;
 	Query	  **sub_action_ptr;
 	acquireLocksOnSubLinks_context context;
+	ListCell   *lc;
 
 	context.for_execute = true;
 
@@ -387,6 +388,23 @@ rewriteRuleAction(Query *parsetree,
 				   PRS2_OLD_VARNO + rt_length, rt_index, 0);
 
 	/*
+	 * Mark any subquery RTEs in the rule action as LATERAL if they contain
+	 * Vars referring to the current query level (references to NEW/OLD).
+	 * Those really are lateral references, but we've historically not
+	 * required users to mark such subqueries with LATERAL explicitly.  But
+	 * the planner will complain if such Vars exist in a non-LATERAL subquery,
+	 * so we have to fix things up here.
+	 */
+	foreach(lc, sub_action->rtable)
+	{
+		RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc);
+
+		if (rte->rtekind == RTE_SUBQUERY && !rte->lateral &&
+			contain_vars_of_level((Node *) rte->subquery, 1))
+			rte->lateral = true;
+	}
+
+	/*
 	 * Generate expanded rtable consisting of main parsetree's rtable plus
 	 * rule action's rtable; this becomes the complete rtable for the rule
 	 * action.  Some of the entries may be unused after we finish rewriting,
@@ -427,8 +445,6 @@ rewriteRuleAction(Query *parsetree,
 	 */
 	if (parsetree->hasSubLinks && !sub_action->hasSubLinks)
 	{
-		ListCell   *lc;
-
 		foreach(lc, parsetree->rtable)
 		{
 			RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc);
@@ -526,8 +542,6 @@ rewriteRuleAction(Query *parsetree,
 	 */
 	if (parsetree->cteList != NIL && sub_action->commandType != CMD_UTILITY)
 	{
-		ListCell   *lc;
-
 		/*
 		 * Annoying implementation restriction: because CTEs are identified by
 		 * name within a cteList, we can't merge a CTE from the original query