From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | pgsql-committers(at)postgresql(dot)org |
Subject: | pgsql: Fix performance problem when building a lossy tidbitmap. |
Date: | 2011-08-20 18:53:37 |
Message-ID: | E1Quqfp-0004Bd-5m@gemulon.postgresql.org |
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Lists: | pgsql-committers |
Fix performance problem when building a lossy tidbitmap.
As pointed out by Sergey Koposov, repeated invocations of tbm_lossify can
make building a large tidbitmap into an O(N^2) operation. To fix, make
sure we remove more than the minimum amount of information per call, and
add a fallback path to behave sanely if we're unable to fit the bitmap
within the requested amount of memory.
This has been wrong since the tidbitmap code was written, so back-patch
to all supported branches.
Branch
------
REL8_2_STABLE
Details
-------
http://git.postgresql.org/pg/commitdiff/6016005118295fdcd97d99a0f372f18a28251c48
Modified Files
--------------
src/backend/nodes/tidbitmap.c | 22 +++++++++++++++++++---
1 files changed, 19 insertions(+), 3 deletions(-)
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