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Make eqsel produce better results for boolean columns,

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and make scalarltsel a little more forgiving at the boundaries of the
known range of a column value.
This commit is contained in:
Tom Lane 2000-02-16 00:59:27 +00:00
parent 9c80cceb02
commit deee4e1612
1 changed files with 12 additions and 9 deletions
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21
src/backend/utils/adt/selfuncs.c
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@ -15,7 +15,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.55 2000/02/15 20:49:21 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.56 2000/02/16 00:59:27 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -144,10 +144,13 @@ eqsel(Oid opid,
selec = 1.0 - commonfrac - nullfrac;
if (selec > commonfrac)
selec = commonfrac;
/* and in fact it's probably less, so apply a fudge
* factor.
/* and in fact it's probably less, so we should apply
* a fudge factor. The only case where we don't is
* for a boolean column, where indeed we have estimated
* the less-common value's frequency exactly!
*/
selec *= 0.5;
if (typid != BOOLOID)
selec *= 0.5;
}
}
else
@ -310,20 +313,20 @@ scalarltsel(Oid opid,
/* If we trusted the stats fully, we could return a small or
* large selec depending on which side of the single data point
* the constant is on. But it seems better to assume that the
* stats are out of date and return a default...
* stats are wrong and return a default...
*/
*result = DEFAULT_INEQ_SEL;
}
else if (val <= low || val >= high)
}
else if (val < low || val > high)
{
/* If given value is outside the statistical range, return a
* small or large value; but not 0.0/1.0 since there is a chance
* the stats are out of date.
*/
if (flag & SEL_RIGHT)
*result = (val <= low) ? 0.01 : 0.99;
*result = (val < low) ? 0.001 : 0.999;
else
*result = (val <= low) ? 0.99 : 0.01;
*result = (val < low) ? 0.999 : 0.001;
}
else
{