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Fix old oversight in join removal logic.

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Commit 9e7e29c75ad441450f9b8287bd51c13521641e3b introduced an Assert that
join removal didn't reduce the eval_at set of any PlaceHolderVar to empty.
At first glance it looks like join_is_removable ensures that's true --- but
actually, the loop in join_is_removable skips PlaceHolderVars that are not
referenced above the join due to be removed.  So, if we don't want any
empty eval_at sets, the right thing to do is to delete any now-unreferenced
PlaceHolderVars from the data structure entirely.

Per fuzz testing by Andreas Seltenreich.  Back-patch to 9.3 where the
aforesaid Assert was added.
This commit is contained in:
Tom Lane 2015-08-06 22:14:07 -04:00
parent e663f75616
commit de0227d8ae
3 changed files with 45 additions and 6 deletions
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20
src/backend/optimizer/plan/analyzejoins.c
View File

@ -464,16 +464,24 @@ remove_rel_from_query(PlannerInfo *root, int relid, Relids joinrelids)
}
/*
* Likewise remove references from PlaceHolderVar data structures.
* Likewise remove references from PlaceHolderVar data structures,
* removing any no-longer-needed placeholders entirely.
*/
foreach(l, root->placeholder_list)
for (l = list_head(root->placeholder_list); l != NULL; l = nextl)
{
PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(l);
phinfo->ph_eval_at = bms_del_member(phinfo->ph_eval_at, relid);
Assert(!bms_is_empty(phinfo->ph_eval_at));
Assert(!bms_is_member(relid, phinfo->ph_lateral));
phinfo->ph_needed = bms_del_member(phinfo->ph_needed, relid);
nextl = lnext(l);
if (bms_is_subset(phinfo->ph_needed, joinrelids))
root->placeholder_list = list_delete_ptr(root->placeholder_list,
phinfo);
else
{
phinfo->ph_eval_at = bms_del_member(phinfo->ph_eval_at, relid);
Assert(!bms_is_empty(phinfo->ph_eval_at));
Assert(!bms_is_member(relid, phinfo->ph_lateral));
phinfo->ph_needed = bms_del_member(phinfo->ph_needed, relid);
}
}
/*

16
src/test/regress/expected/join.out
View File

@ -3862,6 +3862,22 @@ SELECT * FROM
1 | 4567890123456789 | -4567890123456789 | 4567890123456789
(5 rows)
rollback;
-- another join removal bug: we must clean up correctly when removing a PHV
begin;
create temp table uniquetbl (f1 text unique);
explain (costs off)
select t1.* from
uniquetbl as t1
left join (select *, '***'::text as d1 from uniquetbl) t2
on t1.f1 = t2.f1
left join uniquetbl t3
on t2.d1 = t3.f1;
QUERY PLAN
--------------------------
Seq Scan on uniquetbl t1
(1 row)
rollback;
-- bug #8444: we've historically allowed duplicate aliases within aliased JOINs
select * from

15
src/test/regress/sql/join.sql
View File

@ -1247,6 +1247,21 @@ SELECT * FROM
rollback;
-- another join removal bug: we must clean up correctly when removing a PHV
begin;
create temp table uniquetbl (f1 text unique);
explain (costs off)
select t1.* from
uniquetbl as t1
left join (select *, '***'::text as d1 from uniquetbl) t2
on t1.f1 = t2.f1
left join uniquetbl t3
on t2.d1 = t3.f1;
rollback;
-- bug #8444: we've historically allowed duplicate aliases within aliased JOINs
select * from