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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2008-03-09 00:32:09 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2008-03-09 00:32:09 +0000 |
| commit | f4230d29377556a350866f17ebb2e16ac907fa50 (patch) | |
| tree | 76d1422c8b029f26994b5c60ac6ac76587efe08a /src/backend/tcop/postgres.c | |
| parent | 422495d0da79d8a36d6f3700a96c6acddd3e1d50 (diff) | |
| download | postgresql-f4230d29377556a350866f17ebb2e16ac907fa50.tar.gz postgresql-f4230d29377556a350866f17ebb2e16ac907fa50.zip | |
Change patternsel() so that instead of switching from a pure
pattern-examination heuristic method to purely histogram-driven selectivity at
histogram size 100, we compute both estimates and use a weighted average.
The weight put on the heuristic estimate decreases linearly with histogram
size, dropping to zero for 100 or more histogram entries.
Likewise in ltreeparentsel(). After a patch by Greg Stark, though I
reorganized the logic a bit to give the caller of histogram_selectivity()
more control.
Diffstat (limited to 'src/backend/tcop/postgres.c')
0 files changed, 0 insertions, 0 deletions