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Change patternsel (LIKE/regex selectivity estimation) so that if there

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is a large enough histogram, it will use the number of matches in the
histogram to derive a selectivity estimate, rather than the admittedly
pretty bogus heuristics involving examining the pattern contents.  I set
'large enough' at 100, but perhaps we should change that later.  Also
apply the same technique in contrib/ltree's <@ and @> estimator.  Per
discussion with Stefan Kaltenbrunner and Matteo Beccati.
This commit is contained in:
Tom Lane
2006-09-20 19:50:21 +00:00
parent 06b33f0ee8
commit bfd1ffa948
3 changed files with 245 additions and 116 deletions
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5
src/include/utils/selfuncs.h
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@@ -8,7 +8,7 @@
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/utils/selfuncs.h,v 1.34 2006/07/01 22:07:23 tgl Exp $
* $PostgreSQL: pgsql/src/include/utils/selfuncs.h,v 1.35 2006/09/20 19:50:21 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -110,6 +110,9 @@ extern double get_variable_numdistinct(VariableStatData *vardata);
extern double mcv_selectivity(VariableStatData *vardata, FmgrInfo *opproc,
Datum constval, bool varonleft,
double *sumcommonp);
extern double histogram_selectivity(VariableStatData *vardata, FmgrInfo *opproc,
Datum constval, bool varonleft,
int min_hist_size, int n_skip);
extern Pattern_Prefix_Status pattern_fixed_prefix(Const *patt,
Pattern_Type ptype,