Fix PlaceHolderVar mechanism's interaction with outer joins.
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.
Branch
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REL9_0_STABLE
Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=4ec15077b2eaa1f7713e4fff87e220a23c772688
Modified Files
--------------
src/backend/nodes/copyfuncs.c | 1 +
src/backend/nodes/equalfuncs.c | 1 +
src/backend/nodes/outfuncs.c | 1 +
src/backend/optimizer/plan/analyzejoins.c | 2 +
src/backend/optimizer/plan/initsplan.c | 37 +++++
src/backend/optimizer/plan/planmain.c | 23 ++-
src/backend/optimizer/util/placeholder.c | 238 +++++++++++++++++++++++++---
src/include/nodes/relation.h | 17 ++-
src/include/optimizer/placeholder.h | 5 +-
src/test/regress/expected/join.out | 45 ++++++
src/test/regress/sql/join.sql | 40 +++++
11 files changed, 374 insertions(+), 36 deletions(-)