From 510031bfa9eba3726cc93ddf05c1d9217b4e1585 Mon Sep 17 00:00:00 2001 From: Alexander Pyhalov Date: Tue, 18 Mar 2025 13:46:08 +0300 Subject: [PATCH v2] Avoid pulling up restrict infos from subqueries Semi-join joins below left/right join are deparsed as subqueries. Thus, we can't refer to subqueries vars from upper relations. This commit avoids pulling conditions from them. Reported-by: Robins Tharakan Bug: #18852 Discussion: https://postgr.es/m/CAEP4nAzryLd3gwcUpFBAG9MWyDfMRX8ZjuyY2XXjyC_C6k%2B_Zw%40mail.gmail.com Author: Alexander Pyhalov Reviewed-by: Alexander Korotkov Backpatch-through: 17 --- .../postgres_fdw/expected/postgres_fdw.out | 38 +++++++++++++++++++ contrib/postgres_fdw/postgres_fdw.c | 22 +++++++++-- contrib/postgres_fdw/sql/postgres_fdw.sql | 17 +++++++++ 3 files changed, 73 insertions(+), 4 deletions(-) diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out index bb4ed3059c4..d1acee5a5fa 100644 --- a/contrib/postgres_fdw/expected/postgres_fdw.out +++ b/contrib/postgres_fdw/expected/postgres_fdw.out @@ -4936,6 +4936,44 @@ SELECT ft2.*, ft4.* FROM ft2 INNER JOIN ----+----+----+----+----+----+----+----+----+----+---- (0 rows) +-- Semi-join conditions shouldn't pop up as left/right join clauses. +SET enable_material TO off; +EXPLAIN (verbose, costs off) +SELECT x1.c1 FROM + (SELECT * FROM ft2 WHERE EXISTS (SELECT 1 FROM ft4 WHERE ft4.c1 = ft2.c1 AND ft2.c2 < 10)) x1 + RIGHT JOIN + (SELECT * FROM ft2 WHERE EXISTS (SELECT 1 FROM ft4 WHERE ft4.c1 = ft2.c1 AND ft2.c2 < 10)) x2 + ON (x1.c1 = x2.c1) +ORDER BY x1.c1 LIMIT 10; + QUERY PLAN +---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- + Foreign Scan + Output: ft2.c1 + Relations: ((public.ft2 ft2_1) LEFT JOIN ((public.ft2) SEMI JOIN (public.ft4))) SEMI JOIN (public.ft4 ft4_1) + Remote SQL: SELECT s9.c1 FROM ("S 1"."T 1" r6 LEFT JOIN (SELECT r4."C 1" FROM "S 1"."T 1" r4 WHERE ((r4.c2 < 10)) AND EXISTS (SELECT NULL FROM "S 1"."T 3" r5 WHERE ((r4."C 1" = r5.c1)))) s9(c1) ON (((s9.c1 = r6."C 1")))) WHERE ((r6.c2 < 10)) AND EXISTS (SELECT NULL FROM "S 1"."T 3" r7 WHERE ((r6."C 1" = r7.c1))) ORDER BY s9.c1 ASC NULLS LAST LIMIT 10::bigint +(4 rows) + +SELECT x1.c1 FROM + (SELECT * FROM ft2 WHERE EXISTS (SELECT 1 FROM ft4 WHERE ft4.c1 = ft2.c1 AND ft2.c2 < 10)) x1 + RIGHT JOIN + (SELECT * FROM ft2 WHERE EXISTS (SELECT 1 FROM ft4 WHERE ft4.c1 = ft2.c1 AND ft2.c2 < 10)) x2 + ON (x1.c1 = x2.c1) +ORDER BY x1.c1 LIMIT 10; + c1 +---- + 2 + 4 + 6 + 8 + 10 + 12 + 14 + 16 + 18 + 20 +(10 rows) + +RESET enable_material; -- Can't push down semi-join with inner rel vars in targetlist EXPLAIN (verbose, costs off) SELECT ft1.c1 FROM ft1 JOIN ft2 on ft1.c1 = ft2.c1 WHERE diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c index 6beae0fa37f..f9bc7b60939 100644 --- a/contrib/postgres_fdw/postgres_fdw.c +++ b/contrib/postgres_fdw/postgres_fdw.c @@ -5963,16 +5963,30 @@ foreign_join_ok(PlannerInfo *root, RelOptInfo *joinrel, JoinType jointype, break; case JOIN_LEFT: - fpinfo->joinclauses = list_concat(fpinfo->joinclauses, + /* + * When semi-join is involved in the inner or outer part of the + * left join, it's deparsed as a subquery, and we can't refer to + * its vars on the upper level. + */ + if (fpinfo_i->jointype != JOIN_SEMI) + fpinfo->joinclauses = list_concat(fpinfo->joinclauses, fpinfo_i->remote_conds); - fpinfo->remote_conds = list_concat(fpinfo->remote_conds, + if (fpinfo_o->jointype != JOIN_SEMI) + fpinfo->remote_conds = list_concat(fpinfo->remote_conds, fpinfo_o->remote_conds); break; case JOIN_RIGHT: - fpinfo->joinclauses = list_concat(fpinfo->joinclauses, + /* + * When semi-join is involved in the inner or outer part of the + * right join, it's deparsed as a subquery, and we can't refer to + * its vars on the upper level. + */ + if (fpinfo_o->jointype != JOIN_SEMI) + fpinfo->joinclauses = list_concat(fpinfo->joinclauses, fpinfo_o->remote_conds); - fpinfo->remote_conds = list_concat(fpinfo->remote_conds, + if (fpinfo_i->jointype != JOIN_SEMI) + fpinfo->remote_conds = list_concat(fpinfo->remote_conds, fpinfo_i->remote_conds); break; diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql index d45e9f8ab52..ea6287b03fd 100644 --- a/contrib/postgres_fdw/sql/postgres_fdw.sql +++ b/contrib/postgres_fdw/sql/postgres_fdw.sql @@ -1455,6 +1455,23 @@ SELECT ft2.*, ft4.* FROM ft2 INNER JOIN WHERE ft2.c1 > 900 ORDER BY ft2.c1 LIMIT 10; +-- Semi-join conditions shouldn't pop up as left/right join clauses. +SET enable_material TO off; +EXPLAIN (verbose, costs off) +SELECT x1.c1 FROM + (SELECT * FROM ft2 WHERE EXISTS (SELECT 1 FROM ft4 WHERE ft4.c1 = ft2.c1 AND ft2.c2 < 10)) x1 + RIGHT JOIN + (SELECT * FROM ft2 WHERE EXISTS (SELECT 1 FROM ft4 WHERE ft4.c1 = ft2.c1 AND ft2.c2 < 10)) x2 + ON (x1.c1 = x2.c1) +ORDER BY x1.c1 LIMIT 10; +SELECT x1.c1 FROM + (SELECT * FROM ft2 WHERE EXISTS (SELECT 1 FROM ft4 WHERE ft4.c1 = ft2.c1 AND ft2.c2 < 10)) x1 + RIGHT JOIN + (SELECT * FROM ft2 WHERE EXISTS (SELECT 1 FROM ft4 WHERE ft4.c1 = ft2.c1 AND ft2.c2 < 10)) x2 + ON (x1.c1 = x2.c1) +ORDER BY x1.c1 LIMIT 10; +RESET enable_material; + -- Can't push down semi-join with inner rel vars in targetlist EXPLAIN (verbose, costs off) SELECT ft1.c1 FROM ft1 JOIN ft2 on ft1.c1 = ft2.c1 WHERE -- 2.39.5 (Apple Git-154)