Propagate CTE property flags when copying a CTE list into a rule.

rewriteRuleAction() neglected this step, although it was careful to
propagate other similar flags such as hasSubLinks or hasRowSecurity.
Omitting to transfer hasRecursive is just cosmetic at the moment,
but omitting hasModifyingCTE is a live bug, since the executor
certainly looks at that.

The proposed test case only fails back to v10, but since the executor
examines hasModifyingCTE in 9.x as well, I suspect that a test case
could be devised that fails in older branches.  Given the nearness
of the release deadline, though, I'm not going to spend time looking
for a better test.

Report and patch by Greg Nancarrow, cosmetic changes by me

Discussion: https://postgr.es/m/CAJcOf-fAdj=nDKMsRhQzndm-O13NY4dL6xGcEvdX5Xvbbi0V7g@mail.gmail.com

diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
index 987501136974c17acfa76976225f9b391c04da28..9e0e360ff1a33c75e1244e42c76101e95d00c2bd 100644 (file)
--- a/src/backend/rewrite/rewriteHandler.c
+++ b/src/backend/rewrite/rewriteHandler.c
@@ -530,6 +530,9 @@ 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)
        {
@@ -551,6 +554,9 @@ rewriteRuleAction(Query *parsetree,
        /* OK, it's safe to combine the CTE lists */
        sub_action->cteList = list_concat(sub_action->cteList,
                                          copyObject(parsetree->cteList));
+       /* ... and don't forget about the associated flags */
+       sub_action->hasRecursive |= parsetree->hasRecursive;
+       sub_action->hasModifyingCTE |= parsetree->hasModifyingCTE;
    }
 
    /*

diff --git a/src/test/regress/expected/with.out b/src/test/regress/expected/with.out
index 2a2085556bb25a22d8a3bec038b13539789d3254..2680b6394bb98c9943572814d917171101582d86 100644 (file)
--- a/src/test/regress/expected/with.out
+++ b/src/test/regress/expected/with.out
@@ -1672,6 +1672,33 @@ 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 f85645efdee67559a2d3f3b71169acf898937a97..ccf6d06fb9ab5d47e4f9c6354b900764c49a1c72 100644 (file)
--- a/src/test/regress/sql/with.sql
+++ b/src/test/regress/sql/with.sql
@@ -773,6 +773,22 @@ 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