pgsql: Fix performance problem when building a lossy tidbitmap.

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От Tom Lane
Тема pgsql: Fix performance problem when building a lossy tidbitmap.
Дата
Msg-id E1Quqfp-0004BR-0M@gemulon.postgresql.org
обсуждение исходный текст
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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
------
master

Details
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http://git.postgresql.org/pg/commitdiff/08e1eedf247e04a9652d997a74ceb46d889124ba

Modified Files
--------------
src/backend/nodes/tidbitmap.c |   22 +++++++++++++++++++---
1 files changed, 19 insertions(+), 3 deletions(-)


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