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From: Melanie Plageman <melanieplageman@gmail.com>
Date: Fri, 4 Apr 2025 11:47:10 -0400
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 <CAAKRu_bFn5xis9gugrnU3N8O6NN8WYncv5NedHfv3J65m_RZ8w@mail.gmail.com>
Subject: Re: pgsql: Convert 'x IN (VALUES ...)' to 'x = ANY ...' then
 appropriate
To: Alexander Korotkov <akorotkov@postgresql.org>
Cc: pgsql-committers@lists.postgresql.org,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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On Fri, Apr 4, 2025 at 9:17=E2=80=AFAM Alexander Korotkov
<akorotkov@postgresql.org> wrote:
>
> Convert 'x IN (VALUES ...)' to 'x =3D ANY ...' then appropriate
>
> This commit implements the automatic conversion of 'x IN (VALUES ...)' in=
to
> ScalarArrayOpExpr.  That simplifies the query tree, eliminating the appea=
rance
> of an unnecessary join.

I haven't looked at this patch, but it seems likely that it is related
to the recent failures I noticed in CI in the subselect test when the
regress suite is run by 002_pg_upgrade.pl

diff --strip-trailing-cr -U3
C:/cirrus/src/test/regress/expected/subselect.out
C:/cirrus/build/testrun/pg_upgrade/002_pg_upgrade/data/results/subselect.ou=
t
--- C:/cirrus/src/test/regress/expected/subselect.out 2025-04-04
14:44:17.637206600 +0000
+++ C:/cirrus/build/testrun/pg_upgrade/002_pg_upgrade/data/results/subselec=
t.out
2025-04-04 14:47:20.358393500 +0000
@@ -2769,15 +2769,16 @@
 EXPLAIN (COSTS OFF)
 SELECT c.oid,c.relname FROM pg_class c JOIN pg_am a USING (oid)
 WHERE c.oid IN (VALUES (1), (2));
-                          QUERY PLAN
----------------------------------------------------------------
- Hash Join
-   Hash Cond: (a.oid =3D c.oid)
-   ->  Seq Scan on pg_am a
-   ->  Hash
-         ->  Index Scan using pg_class_oid_index on pg_class c
-               Index Cond: (oid =3D ANY ('{1,2}'::oid[]))
-(6 rows)
+                       QUERY PLAN
+---------------------------------------------------------
+ Merge Join
+   Merge Cond: (c.oid =3D a.oid)
+   ->  Index Scan using pg_class_oid_index on pg_class c
+         Index Cond: (oid =3D ANY ('{1,2}'::oid[]))
+   ->  Sort
+         Sort Key: a.oid
+         ->  Seq Scan on pg_am a
+(7 rows)