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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2002-12-26 23:38:42 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2002-12-26 23:38:42 +0000 |
| commit | f772e6cbf7f24245d59c4429f24a9c8cc4a9e38c (patch) | |
| tree | da03f9dcb146106dd654c2cf811d1a86b1257da8 /src | |
| parent | 1dfbbd51e778c924b2958c69308adf02681d0801 (diff) | |
| download | postgresql-f772e6cbf7f24245d59c4429f24a9c8cc4a9e38c.tar.gz postgresql-f772e6cbf7f24245d59c4429f24a9c8cc4a9e38c.zip | |
Clamp the output of estimate_hash_bucketsize() to a sane range;
per example from Bruno Wolff in which it produced a silly result.
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/optimizer/path/costsize.c | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c index 5feaed49158..a19dd92c826 100644 --- a/src/backend/optimizer/path/costsize.c +++ b/src/backend/optimizer/path/costsize.c @@ -42,7 +42,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.96 2002/12/14 00:17:55 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.97 2002/12/26 23:38:42 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -1164,6 +1164,16 @@ estimate_hash_bucketsize(Query *root, Var *var) if (avgfreq > 0.0 && mcvfreq > avgfreq) estfract *= mcvfreq / avgfreq; + /* + * Clamp bucketsize to sane range (the above adjustment could easily + * produce an out-of-range result). We set the lower bound a little + * above zero, since zero isn't a very sane result. + */ + if (estfract < 1.0e-6) + estfract = 1.0e-6; + else if (estfract > 1.0) + estfract = 1.0; + ReleaseSysCache(tuple); return (Selectivity) estfract; |