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Commit8d367a4

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Fix alias matching in transformLockingClause().
When locking a specific named relation for a FOR [KEY] UPDATE/SHAREclause, transformLockingClause() finds the relation to lock byscanning 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 agenerated eref->aliasname of "unnamed_join" that is not visible as arelation name in the parse namespace. Such an RTE needs to be skipped,otherwise it might be found in preference to a regular base relationwith a user-supplied alias of "unnamed_join", preventing it from beinglocked.In addition, if a join RTE doesn't have a user-supplied alias, butdoes have a join_using_alias, then the RTE needs to be matched usingthat alias rather than the generated eref->aliasname, otherwise amisleading "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 backto 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
1 parent82699ed commit8d367a4

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3 files changed

+73
-1
lines changed

3 files changed

+73
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lines changed

‎src/backend/parser/analyze.c

Lines changed: 18 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3291,11 +3291,28 @@ transformLockingClause(ParseState *pstate, Query *qry, LockingClause *lc,
32913291
foreach(rt,qry->rtable)
32923292
{
32933293
RangeTblEntry*rte= (RangeTblEntry*)lfirst(rt);
3294+
char*rtename;
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32953296
++i;
32963297
if (!rte->inFromCl)
32973298
continue;
3298-
if (strcmp(rte->eref->aliasname,thisrel->relname)==0)
3299+
3300+
/*
3301+
* A join RTE without an alias is not visible as a relation
3302+
* name and needs to be skipped (otherwise it might hide a
3303+
* base relation with the same name), except if it has a USING
3304+
* alias, which *is* visible.
3305+
*/
3306+
if (rte->rtekind==RTE_JOIN&&rte->alias==NULL)
3307+
{
3308+
if (rte->join_using_alias==NULL)
3309+
continue;
3310+
rtename=rte->join_using_alias->aliasname;
3311+
}
3312+
else
3313+
rtename=rte->eref->aliasname;
3314+
3315+
if (strcmp(rtename,thisrel->relname)==0)
32993316
{
33003317
switch (rte->rtekind)
33013318
{

‎src/test/regress/expected/join.out

Lines changed: 33 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2501,6 +2501,39 @@ ERROR: column t1.x does not exist
25012501
LINE 1: select t1.x from t1 join t3 on (t1.a = t3.x);
25022502
^
25032503
HINT: Perhaps you meant to reference the column "t3.x".
2504+
-- Test matching of locking clause with wrong alias
2505+
select t1.*, t2.*, unnamed_join.* from
2506+
t1 join t2 on (t1.a = t2.a), t3 as unnamed_join
2507+
for update of unnamed_join;
2508+
a | b | a | b | x | y
2509+
---+---+---+---+---+---
2510+
(0 rows)
2511+
2512+
select foo.*, unnamed_join.* from
2513+
t1 join t2 using (a) as foo, t3 as unnamed_join
2514+
for update of unnamed_join;
2515+
a | x | y
2516+
---+---+---
2517+
(0 rows)
2518+
2519+
select foo.*, unnamed_join.* from
2520+
t1 join t2 using (a) as foo, t3 as unnamed_join
2521+
for update of foo;
2522+
ERROR: FOR UPDATE cannot be applied to a join
2523+
LINE 3: for update of foo;
2524+
^
2525+
select bar.*, unnamed_join.* from
2526+
(t1 join t2 using (a) as foo) as bar, t3 as unnamed_join
2527+
for update of foo;
2528+
ERROR: relation "foo" in FOR UPDATE clause not found in FROM clause
2529+
LINE 3: for update of foo;
2530+
^
2531+
select bar.*, unnamed_join.* from
2532+
(t1 join t2 using (a) as foo) as bar, t3 as unnamed_join
2533+
for update of bar;
2534+
ERROR: FOR UPDATE cannot be applied to a join
2535+
LINE 3: for update of bar;
2536+
^
25042537
--
25052538
-- regression test for 8.1 merge right join bug
25062539
--

‎src/test/regress/sql/join.sql

Lines changed: 22 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -520,6 +520,28 @@ select * from t1 left join t2 on (t1.a = t2.a);
520520

521521
selectt1.xfrom t1join t3on (t1.a=t3.x);
522522

523+
-- Test matching of locking clause with wrong alias
524+
525+
select t1.*, t2.*, unnamed_join.*from
526+
t1join t2on (t1.a=t2.a), t3as unnamed_join
527+
forupdate of unnamed_join;
528+
529+
select foo.*, unnamed_join.*from
530+
t1join t2 using (a)as foo, t3as unnamed_join
531+
forupdate of unnamed_join;
532+
533+
select foo.*, unnamed_join.*from
534+
t1join t2 using (a)as foo, t3as unnamed_join
535+
forupdate of foo;
536+
537+
select bar.*, unnamed_join.*from
538+
(t1join t2 using (a)as foo)as bar, t3as unnamed_join
539+
forupdate of foo;
540+
541+
select bar.*, unnamed_join.*from
542+
(t1join t2 using (a)as foo)as bar, t3as unnamed_join
543+
forupdate of bar;
544+
523545
--
524546
-- regression test for 8.1 merge right join bug
525547
--

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