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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2000-05-26 17:19:15 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2000-05-26 17:19:15 +0000 |
| commit | b71761d2808a5b2d841bbccf193e326bdca0a52d (patch) | |
| tree | 071f38de63a6bbf52597045f71472acc91e6e421 /src/backend/utils/adt/selfuncs.c | |
| parent | be6e7717db53812248d89c2ee798bb80e54a00ee (diff) | |
| download | postgresql-b71761d2808a5b2d841bbccf193e326bdca0a52d.tar.gz postgresql-b71761d2808a5b2d841bbccf193e326bdca0a52d.zip | |
Reduce eqsel()'s fudge-factor for estimating the frequency of values
other than the most common value in a column. We had had 0.5, make it
0.1 to make it more likely that an indexscan will be chosen. Really
need better statistics instead, but this should stem the bleeding
meanwhile ...
Diffstat (limited to 'src/backend/utils/adt/selfuncs.c')
| -rw-r--r-- | src/backend/utils/adt/selfuncs.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c index a1405602ee4..4718dc668a7 100644 --- a/src/backend/utils/adt/selfuncs.c +++ b/src/backend/utils/adt/selfuncs.c @@ -15,7 +15,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.65 2000/04/16 04:41:02 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.66 2000/05/26 17:19:15 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -55,6 +55,9 @@ /* default selectivity estimate for pattern-match operators such as LIKE */ #define DEFAULT_MATCH_SEL 0.01 +/* "fudge factor" for estimating frequency of not-most-common values */ +#define NOT_MOST_COMMON_RATIO 0.1 + static bool convert_to_scalar(Datum value, Oid valuetypid, double *scaledvalue, Datum lobound, Datum hibound, Oid boundstypid, double *scaledlobound, double *scaledhibound); @@ -190,7 +193,7 @@ eqsel(Oid opid, * exactly! */ if (typid != BOOLOID) - selec *= 0.5; + selec *= NOT_MOST_COMMON_RATIO; } } else @@ -209,7 +212,7 @@ eqsel(Oid opid, * and in fact it's probably less, so apply a fudge * factor. */ - selec *= 0.5; + selec *= NOT_MOST_COMMON_RATIO; } /* result should be in range, but make sure... */ |