From: Dean Rasheed <dean.a.rasheed@gmail.com>
Date: Thu, 7 Jul 2022 12:07:51 +0000 (+0100)
Subject: Fix alias matching in transformLockingClause().
X-Git-Tag: REL_10_22~35
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8ace122d438a405cbac6352296d802e3fc904295;p=thirdparty%2Fpostgresql.git

Fix alias matching in transformLockingClause().

When locking a specific named relation for a FOR [KEY] UPDATE/SHARE
clause, transformLockingClause() finds the relation to lock by
scanning the rangetable for an RTE with a matching eref->aliasname.
However, it failed to account for the visibility rules of a join RTE.

If a join RTE doesn't have a user-supplied alias, it will have a
generated eref->aliasname of "unnamed_join" that is not visible as a
relation name in the parse namespace. Such an RTE needs to be skipped,
otherwise it might be found in preference to a regular base relation
with a user-supplied alias of "unnamed_join", preventing it from being
locked.

In addition, if a join RTE doesn't have a user-supplied alias, but
does have a join_using_alias, then the RTE needs to be matched using
that alias rather than the generated eref->aliasname, otherwise a
misleading "relation not found" error will be reported rather than a
"join cannot be locked" error.

Backpatch all the way, except for the second part which only goes back
to 14, where JOIN USING aliases were added.

Dean Rasheed, reviewed by Tom Lane.

Discussion: https://postgr.es/m/CAEZATCUY_KOBnqxbTSPf=7fz9HWPnZ5Xgb9SwYzZ8rFXe7nb=w@mail.gmail.com
---

diff --git a/src/backend/parser/analyze.c b/src/backend/parser/analyze.c
index 14be0882578..a7e2120e0dc 100644
--- a/src/backend/parser/analyze.c
+++ b/src/backend/parser/analyze.c
@@ -2783,6 +2783,15 @@ transformLockingClause(ParseState *pstate, Query *qry, LockingClause *lc,
 				++i;
 				if (!rte->inFromCl)
 					continue;
+
+				/*
+				 * A join RTE without an alias is not visible as a relation
+				 * name and needs to be skipped (otherwise it might hide a
+				 * base relation with the same name).
+				 */
+				if (rte->rtekind == RTE_JOIN && rte->alias == NULL)
+					continue;
+
 				if (strcmp(rte->eref->aliasname, thisrel->relname) == 0)
 				{
 					switch (rte->rtekind)
diff --git a/src/test/regress/expected/join.out b/src/test/regress/expected/join.out
index e8f7a13a0a8..4dd78e91e50 100644
--- a/src/test/regress/expected/join.out
+++ b/src/test/regress/expected/join.out
@@ -2412,6 +2412,14 @@ ERROR:  column t1.x does not exist
 LINE 1: select t1.x from t1 join t3 on (t1.a = t3.x);
                ^
 HINT:  Perhaps you meant to reference the column "t3.x".
+-- Test matching of locking clause with wrong alias
+select t1.*, t2.*, unnamed_join.* from
+  t1 join t2 on (t1.a = t2.a), t3 as unnamed_join
+  for update of unnamed_join;
+ a | b | a | b | x | y 
+---+---+---+---+---+---
+(0 rows)
+
 --
 -- regression test for 8.1 merge right join bug
 --
diff --git a/src/test/regress/sql/join.sql b/src/test/regress/sql/join.sql
index 9404ec86bb6..b11e9280128 100644
--- a/src/test/regress/sql/join.sql
+++ b/src/test/regress/sql/join.sql
@@ -487,6 +487,12 @@ select * from t1 left join t2 on (t1.a = t2.a);
 
 select t1.x from t1 join t3 on (t1.a = t3.x);
 
+-- Test matching of locking clause with wrong alias
+
+select t1.*, t2.*, unnamed_join.* from
+  t1 join t2 on (t1.a = t2.a), t3 as unnamed_join
+  for update of unnamed_join;
+
 --
 -- regression test for 8.1 merge right join bug
 --