From cb0dea0115dc108d2b5c7fb4bd6310c1d742cac0 Mon Sep 17 00:00:00 2001
From: Takayuki Tsunakawa <tsunakawa.takay@fujitsu.com>
Date: Thu, 20 May 2021 23:01:46 +0900
Subject: [PATCH v3] propagate CTE property flags in rewriter

---
 src/backend/rewrite/rewriteHandler.c | 14 ++++++++++----
 src/test/regress/expected/with.out   | 27 +++++++++++++++++++++++++++
 src/test/regress/sql/with.sql        | 16 ++++++++++++++++
 3 files changed, 53 insertions(+), 4 deletions(-)

diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
index 88a9e95..09bd2f3 100644
--- a/src/backend/rewrite/rewriteHandler.c
+++ b/src/backend/rewrite/rewriteHandler.c
@@ -467,7 +467,7 @@ rewriteRuleAction(Query *parsetree,
 	 * this is a no-op because RLS conditions aren't added till later, but it
 	 * seems like good future-proofing to do this anyway.)
 	 */
-	sub_action->hasRowSecurity |= parsetree->hasRowSecurity;
+	sub_action->hasRowSecurity = parsetree->hasRowSecurity;
 
 	/*
 	 * Each rule action's jointree should be the main parsetree's jointree
@@ -524,7 +524,7 @@ rewriteRuleAction(Query *parsetree,
 	 * If the original query has any CTEs, copy them into the rule action. But
 	 * we don't need them for a utility action.
 	 */
-	if (parsetree->cteList != NIL && sub_action->commandType != CMD_UTILITY)
+	if (parsetree->cteList != NIL && rule_action->commandType != CMD_UTILITY)
 	{
 		ListCell   *lc;
 
@@ -535,13 +535,16 @@ rewriteRuleAction(Query *parsetree,
 		 *
 		 * This could possibly be fixed by using some sort of internally
 		 * generated ID, instead of names, to link CTE RTEs to their CTEs.
+		 * However, decompiling the results would be quite confusing; note the
+		 * merge of hasRecursive flags below, which could change the apparent
+		 * semantics of such redundantly-named CTEs.
 		 */
 		foreach(lc, parsetree->cteList)
 		{
 			CommonTableExpr *cte = (CommonTableExpr *) lfirst(lc);
 			ListCell   *lc2;
 
-			foreach(lc2, sub_action->cteList)
+			foreach(lc2, rule_action->cteList)
 			{
 				CommonTableExpr *cte2 = (CommonTableExpr *) lfirst(lc2);
 
@@ -554,8 +557,11 @@ rewriteRuleAction(Query *parsetree,
 		}
 
 		/* OK, it's safe to combine the CTE lists */
-		sub_action->cteList = list_concat(sub_action->cteList,
+		rule_action->cteList = list_concat(rule_action->cteList,
 										  copyObject(parsetree->cteList));
+		/* ... and don't forget about the associated flags */
+		rule_action->hasRecursive = parsetree->hasRecursive;
+		rule_action->hasModifyingCTE = parsetree->hasModifyingCTE;
 	}
 
 	/*
diff --git a/src/test/regress/expected/with.out b/src/test/regress/expected/with.out
index 584bdc6..a1c5844 100644
--- a/src/test/regress/expected/with.out
+++ b/src/test/regress/expected/with.out
@@ -2397,6 +2397,33 @@ SELECT * FROM bug6051_2;
  3
 (3 rows)
 
+-- silly example to verify that hasModifyingCTE flag is propagated
+CREATE TEMP TABLE bug6051_3 AS
+  select a from generate_series(11,13) as a;
+CREATE RULE bug6051_3_ins AS ON INSERT TO bug6051_3 DO INSTEAD
+  SELECT i FROM bug6051_2;
+BEGIN; SET LOCAL force_parallel_mode = on;
+WITH t1 AS ( DELETE FROM bug6051_3 RETURNING * )
+  INSERT INTO bug6051_3 SELECT * FROM t1;
+ i 
+---
+ 1
+ 2
+ 3
+ 1
+ 2
+ 3
+ 1
+ 2
+ 3
+(9 rows)
+
+COMMIT;
+SELECT * FROM bug6051_3;
+ a 
+---
+(0 rows)
+
 -- a truly recursive CTE in the same list
 WITH RECURSIVE t(a) AS (
 	SELECT 0
diff --git a/src/test/regress/sql/with.sql b/src/test/regress/sql/with.sql
index 1a9bdc9..d9b4d06 100644
--- a/src/test/regress/sql/with.sql
+++ b/src/test/regress/sql/with.sql
@@ -1126,6 +1126,22 @@ INSERT INTO bug6051 SELECT * FROM t1;
 SELECT * FROM bug6051;
 SELECT * FROM bug6051_2;
 
+-- silly example to verify that hasModifyingCTE flag is propagated
+CREATE TEMP TABLE bug6051_3 AS
+  select a from generate_series(11,13) as a;
+
+CREATE RULE bug6051_3_ins AS ON INSERT TO bug6051_3 DO INSTEAD
+  SELECT i FROM bug6051_2;
+
+BEGIN; SET LOCAL force_parallel_mode = on;
+
+WITH t1 AS ( DELETE FROM bug6051_3 RETURNING * )
+  INSERT INTO bug6051_3 SELECT * FROM t1;
+
+COMMIT;
+
+SELECT * FROM bug6051_3;
+
 -- a truly recursive CTE in the same list
 WITH RECURSIVE t(a) AS (
 	SELECT 0
-- 
2.10.1