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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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5
src/include/optimizer/placeholder.h
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@@ -21,7 +21,10 @@ extern PlaceHolderVar *make_placeholder_expr(PlannerInfo *root, Expr *expr,
Relids phrels);
extern PlaceHolderInfo *find_placeholder_info(PlannerInfo *root,
PlaceHolderVar *phv);
extern void fix_placeholder_eval_levels(PlannerInfo *root);
extern void find_placeholders_in_jointree(PlannerInfo *root);
extern void update_placeholder_eval_levels(PlannerInfo *root,
SpecialJoinInfo *new_sjinfo);
extern void fix_placeholder_input_needed_levels(PlannerInfo *root);
extern void add_placeholders_to_base_rels(PlannerInfo *root);
extern void add_placeholders_to_joinrel(PlannerInfo *root,
RelOptInfo *joinrel);