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 ab36406753d3d27aab6455faebc246abcf5c465f..333be34fc46ef9c26289820df59c0945eb0b8bec 100644 (file)
--- a/src/backend/parser/analyze.c
+++ b/src/backend/parser/analyze.c
@@ -3245,11 +3245,28 @@ transformLockingClause(ParseState *pstate, Query *qry, LockingClause *lc,
            foreach(rt, qry->rtable)
            {
                RangeTblEntry *rte = (RangeTblEntry *) lfirst(rt);
+               char       *rtename;
 
                ++i;
                if (!rte->inFromCl)
                    continue;
-               if (strcmp(rte->eref->aliasname, thisrel->relname) == 0)
+
+               /*
+                * 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), except if it has a USING
+                * alias, which *is* visible.
+                */
+               if (rte->rtekind == RTE_JOIN && rte->alias == NULL)
+               {
+                   if (rte->join_using_alias == NULL)
+                       continue;
+                   rtename = rte->join_using_alias->aliasname;
+               }
+               else
+                   rtename = rte->eref->aliasname;
+
+               if (strcmp(rtename, thisrel->relname) == 0)
                {
                    switch (rte->rtekind)
                    {

diff --git a/src/test/regress/expected/join.out b/src/test/regress/expected/join.out
index 3cb1b383dc1fe5001ede6f61ccb536dc83dfa32c..5c56304504f56719ab8a4e93006e978337bfe94b 100644 (file)
--- a/src/test/regress/expected/join.out
+++ b/src/test/regress/expected/join.out
@@ -2501,6 +2501,39 @@ 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)
+
+select foo.*, unnamed_join.* from
+  t1 join t2 using (a) as foo, t3 as unnamed_join
+  for update of unnamed_join;
+ a | x | y 
+---+---+---
+(0 rows)
+
+select foo.*, unnamed_join.* from
+  t1 join t2 using (a) as foo, t3 as unnamed_join
+  for update of foo;
+ERROR:  FOR UPDATE cannot be applied to a join
+LINE 3:   for update of foo;
+                        ^
+select bar.*, unnamed_join.* from
+  (t1 join t2 using (a) as foo) as bar, t3 as unnamed_join
+  for update of foo;
+ERROR:  relation "foo" in FOR UPDATE clause not found in FROM clause
+LINE 3:   for update of foo;
+                        ^
+select bar.*, unnamed_join.* from
+  (t1 join t2 using (a) as foo) as bar, t3 as unnamed_join
+  for update of bar;
+ERROR:  FOR UPDATE cannot be applied to a join
+LINE 3:   for update of bar;
+                        ^
 --
 -- 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 c451efa958929d34ea26c28424911119d7713592..eb24a727e7399464ead34d8c7615b446e86aad76 100644 (file)
--- a/src/test/regress/sql/join.sql
+++ b/src/test/regress/sql/join.sql
@@ -520,6 +520,28 @@ 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;
+
+select foo.*, unnamed_join.* from
+  t1 join t2 using (a) as foo, t3 as unnamed_join
+  for update of unnamed_join;
+
+select foo.*, unnamed_join.* from
+  t1 join t2 using (a) as foo, t3 as unnamed_join
+  for update of foo;
+
+select bar.*, unnamed_join.* from
+  (t1 join t2 using (a) as foo) as bar, t3 as unnamed_join
+  for update of foo;
+
+select bar.*, unnamed_join.* from
+  (t1 join t2 using (a) as foo) as bar, t3 as unnamed_join
+  for update of bar;
+
 --
 -- regression test for 8.1 merge right join bug
 --