0003-Make-replace_relid-leave-argument-unmodified-v2.patch

From c197405fbae7f6b8abe217fbfab8c4882a872229 Mon Sep 17 00:00:00 2001
From: Alexander Korotkov <akorotkov@postgresql.org>
Date: Fri, 24 Nov 2023 14:57:27 +0200
Subject: [PATCH 3/3] Make replace_relid() leave argument unmodified

There are a lot of situations when we share the same pointer to a Bitmapset
structure across different places.  In order to evade undesirable side effects
replace_relid() function should always return a copy.
---
 src/backend/optimizer/plan/analyzejoins.c | 11 ++++++++---
 src/test/regress/expected/join.out        | 15 +++++++++++++++
 src/test/regress/sql/join.sql             |  6 ++++++
 3 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/src/backend/optimizer/plan/analyzejoins.c b/src/backend/optimizer/plan/analyzejoins.c
index b9be19a687f..75e4ebc64a2 100644
--- a/src/backend/optimizer/plan/analyzejoins.c
+++ b/src/backend/optimizer/plan/analyzejoins.c
@@ -1511,6 +1511,10 @@ replace_varno_walker(Node *node, ReplaceVarnoContext *ctx)
 
 /*
  * Substitute newId by oldId in relids.
+ *
+ * We must make a copy of the original Bitmapset before making any
+ * modifications, because the same pointer to it might be shared among
+ * different places.
  */
 static Bitmapset *
 replace_relid(Relids relids, int oldId, int newId)
@@ -1518,12 +1522,13 @@ replace_relid(Relids relids, int oldId, int newId)
 	if (oldId < 0)
 		return relids;
 
+	/* Delete relid without substitution. */
 	if (newId < 0)
-		/* Delete relid without substitution. */
-		return bms_del_member(relids, oldId);
+		return bms_del_member(bms_copy(relids), oldId);
 
+	/* Substitute newId for oldId. */
 	if (bms_is_member(oldId, relids))
-		return bms_add_member(bms_del_member(relids, oldId), newId);
+		return bms_add_member(bms_del_member(bms_copy(relids), oldId), newId);
 
 	return relids;
 }
diff --git a/src/test/regress/expected/join.out b/src/test/regress/expected/join.out
index 2c73270143b..5ceecc44132 100644
--- a/src/test/regress/expected/join.out
+++ b/src/test/regress/expected/join.out
@@ -6836,6 +6836,21 @@ select * from emp1 t1 join emp1 t2 on t1.id = t2.id left join
    ->  Function Scan on generate_series t3
 (6 rows)
 
+-- Check that SJE replaces join clauses involving the removed rel correctly
+explain (costs off)
+select * from emp1 t1
+   inner join emp1 t2 on t1.id = t2.id
+    left join emp1 t3 on t1.id > 1 and t1.id < 2;
+                  QUERY PLAN                  
+----------------------------------------------
+ Nested Loop Left Join
+   Join Filter: ((t2.id > 1) AND (t2.id < 2))
+   ->  Seq Scan on emp1 t2
+         Filter: (id IS NOT NULL)
+   ->  Materialize
+         ->  Seq Scan on emp1 t3
+(6 rows)
+
 -- We can remove the join even if we find the join can't duplicate rows and
 -- the base quals of each side are different.  In the following case we end up
 -- moving quals over to s1 to make it so it can't match any rows.
diff --git a/src/test/regress/sql/join.sql b/src/test/regress/sql/join.sql
index 8a8a63bd2f1..c3ec340e2da 100644
--- a/src/test/regress/sql/join.sql
+++ b/src/test/regress/sql/join.sql
@@ -2606,6 +2606,12 @@ explain (costs off)
 select * from emp1 t1 join emp1 t2 on t1.id = t2.id left join
     lateral (select t1.id as t1id, * from generate_series(1,1) t3) s on true;
 
+-- Check that SJE replaces join clauses involving the removed rel correctly
+explain (costs off)
+select * from emp1 t1
+   inner join emp1 t2 on t1.id = t2.id
+    left join emp1 t3 on t1.id > 1 and t1.id < 2;
+
 -- We can remove the join even if we find the join can't duplicate rows and
 -- the base quals of each side are different.  In the following case we end up
 -- moving quals over to s1 to make it so it can't match any rows.
-- 
2.39.3 (Apple Git-145)