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 a309dc36665b4cab5bf97c28f6c054ceccc05838..447db2863d53ec15e5bfb231e6e2fe5cf2ba69f0 100644 (file)
--- a/src/backend/parser/analyze.c
+++ b/src/backend/parser/analyze.c
@@ -2818,6 +2818,15 @@ 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 c8d3716a15eb9c000b8dccf3ae417c70bd1c0210..3cef1b3525ca44e1b4f018da86a8d754533f70b7 100644 (file)
--- a/src/test/regress/expected/join.out
+++ b/src/test/regress/expected/join.out
@@ -2449,6 +2449,14 @@ 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 691fae38d50425c56067f4c6aa341d3f307b9759..7a04d67a1451f2770e72a5396bfe8de6992bbf80 100644 (file)
--- a/src/test/regress/sql/join.sql
+++ b/src/test/regress/sql/join.sql
@@ -509,6 +509,12 @@ 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
 --