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
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REL9_1_STABLE
Details
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http://git.postgresql.org/pg/commitdiff/548d1f752be7a11e240f1eadd4f9987a7b9793c5
Modified Files
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src/backend/nodes/tidbitmap.c | 22 +++++++++++++++++++---
1 files changed, 19 insertions(+), 3 deletions(-)