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Fix PlaceHolderVar mechanism's interaction with outer joins.

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The point of a PlaceHolderVar is to allow a non-strict expression to be
evaluated below an outer join, after which its value bubbles up like a Var
and can be forced to NULL when the outer join's semantics require that.
However, there was a serious design oversight in that, namely that we
didn't ensure that there was actually a correct place in the plan tree
to evaluate the placeholder :-(.  It may be necessary to delay evaluation
of an outer join to ensure that a placeholder that should be evaluated
below the join can be evaluated there.  Per recent bug report from Kirill
Simonov.

Back-patch to 8.4 where the PlaceHolderVar mechanism was introduced.
This commit is contained in:
Tom Lane
2010-09-28 12:08:56 -04:00
parent 9c5f4f6cb5
commit eb22950510
11 changed files with 374 additions and 36 deletions
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2
src/backend/optimizer/plan/analyzejoins.c
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@ -396,6 +396,8 @@ remove_rel_from_query(PlannerInfo *root, int relid, Relids joinrelids)
phinfo->ph_eval_at = bms_add_member(phinfo->ph_eval_at, relid);
phinfo->ph_needed = bms_del_member(phinfo->ph_needed, relid);
/* ph_may_need probably isn't used after this, but fix it anyway */
phinfo->ph_may_need = bms_del_member(phinfo->ph_may_need, relid);
}
/*