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Fix old oversight in join removal logic.

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Commit 9e7e29c75a 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 0d4913509b
commit de5edc660a
3 changed files with 45 additions and 6 deletions
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20
src/backend/optimizer/plan/analyzejoins.c
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@@ -382,16 +382,24 @@ 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);
}
}
/*