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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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1
src/backend/nodes/copyfuncs.c
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@ -1806,6 +1806,7 @@ _copyPlaceHolderInfo(PlaceHolderInfo *from)
COPY_NODE_FIELD(ph_var);
COPY_BITMAPSET_FIELD(ph_eval_at);
COPY_BITMAPSET_FIELD(ph_needed);
COPY_BITMAPSET_FIELD(ph_may_need);
COPY_SCALAR_FIELD(ph_width);
return newnode;

1
src/backend/nodes/equalfuncs.c
View File

@ -838,6 +838,7 @@ _equalPlaceHolderInfo(PlaceHolderInfo *a, PlaceHolderInfo *b)
COMPARE_NODE_FIELD(ph_var);
COMPARE_BITMAPSET_FIELD(ph_eval_at);
COMPARE_BITMAPSET_FIELD(ph_needed);
COMPARE_BITMAPSET_FIELD(ph_may_need);
COMPARE_SCALAR_FIELD(ph_width);
return true;

1
src/backend/nodes/outfuncs.c
View File

@ -1768,6 +1768,7 @@ _outPlaceHolderInfo(StringInfo str, PlaceHolderInfo *node)
WRITE_NODE_FIELD(ph_var);
WRITE_BITMAPSET_FIELD(ph_eval_at);
WRITE_BITMAPSET_FIELD(ph_needed);
WRITE_BITMAPSET_FIELD(ph_may_need);
WRITE_INT_FIELD(ph_width);
}