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author | Tom Lane <tgl@sss.pgh.pa.us> | 2008-08-17 19:40:11 +0000 |
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committer | Tom Lane <tgl@sss.pgh.pa.us> | 2008-08-17 19:40:11 +0000 |
commit | 719012e013f10f72938520c46889c52df40fa329 (patch) | |
tree | a87f2a1051080d6c56628a6956d508b00609afcc /src/backend/tcop/postgres.c | |
parent | f2689e421d7ca0a103e33f5b92bb0676c80e1d04 (diff) | |
download | postgresql-719012e013f10f72938520c46889c52df40fa329.tar.gz postgresql-719012e013f10f72938520c46889c52df40fa329.zip |
Add some defenses against constant-FALSE outer join conditions. Since
eval_const_expressions will generally throw away anything that's ANDed with
constant FALSE, what we're left with given an example like
select * from tenk1 a where (unique1,0) in (select unique2,1 from tenk1 b);
is a cartesian product computation, which is really not acceptable.
This is a regression in CVS HEAD compared to previous releases, which were
able to notice the impossible join condition in this case --- though not in
some related cases that are also improved by this patch, such as
select * from tenk1 a left join tenk1 b on (a.unique1=b.unique2 and 0=1);
Fix by skipping evaluation of the appropriate side of the outer join in
cases where it's demonstrably unnecessary.
Diffstat (limited to 'src/backend/tcop/postgres.c')
0 files changed, 0 insertions, 0 deletions