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If we cannot get a real estimate for the selectivity of a range query,

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use a default value that's fairly small.  We were generating a result
of about 0.1, but I think 0.01 is probably better --- want to encourage
use of an indexscan in this situation.
This commit is contained in:
Tom Lane
2000-03-23 00:58:36 +00:00
parent cad764f349
commit 1afaa2557a
1 changed files with 5 additions and 3 deletions
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8
src/backend/optimizer/path/clausesel.c
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@ -8,7 +8,7 @@
* *
* *
* IDENTIFICATION * IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/clausesel.c,v 1.31 2000/03/17 02:36:14 tgl Exp $ * $Header: /cvsroot/pgsql/src/backend/optimizer/path/clausesel.c,v 1.32 2000/03/23 00:58:36 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -194,9 +194,11 @@ clauselist_selectivity(Query *root,
else else
{ {
/* One or both is probably a default estimate, /* One or both is probably a default estimate,
* so punt and just merge them in generically. * so supply a default estimate for the selectivity
* of the range query. We rather optimistically assume
* that the range is tight...
*/ */
s1 *= rqlist->hibound * rqlist->lobound; s1 *= 0.01;
} }
} }
else else