diff options
Diffstat (limited to 'src/include/utils/selfuncs.h')
| -rw-r--r-- | src/include/utils/selfuncs.h | 45 |
1 files changed, 44 insertions, 1 deletions
diff --git a/src/include/utils/selfuncs.h b/src/include/utils/selfuncs.h index 84edb000f47..185f848f584 100644 --- a/src/include/utils/selfuncs.h +++ b/src/include/utils/selfuncs.h @@ -8,7 +8,7 @@ * Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $PostgreSQL: pgsql/src/include/utils/selfuncs.h,v 1.19 2004/08/29 05:06:59 momjian Exp $ + * $PostgreSQL: pgsql/src/include/utils/selfuncs.h,v 1.20 2004/11/09 00:34:46 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -19,6 +19,49 @@ #include "nodes/parsenodes.h" +/* + * Note: the default selectivity estimates are not chosen entirely at random. + * We want them to be small enough to ensure that indexscans will be used if + * available, for typical table densities of ~100 tuples/page. Thus, for + * example, 0.01 is not quite small enough, since that makes it appear that + * nearly all pages will be hit anyway. Also, since we sometimes estimate + * eqsel as 1/num_distinct, we probably want DEFAULT_NUM_DISTINCT to equal + * 1/DEFAULT_EQ_SEL. + */ + +/* default selectivity estimate for equalities such as "A = b" */ +#define DEFAULT_EQ_SEL 0.005 + +/* default selectivity estimate for inequalities such as "A < b" */ +#define DEFAULT_INEQ_SEL 0.3333333333333333 + +/* default selectivity estimate for range inequalities "A > b AND A < c" */ +#define DEFAULT_RANGE_INEQ_SEL 0.005 + +/* default selectivity estimate for pattern-match operators such as LIKE */ +#define DEFAULT_MATCH_SEL 0.005 + +/* default number of distinct values in a table */ +#define DEFAULT_NUM_DISTINCT 200 + +/* default selectivity estimate for boolean and null test nodes */ +#define DEFAULT_UNK_SEL 0.005 +#define DEFAULT_NOT_UNK_SEL (1.0 - DEFAULT_UNK_SEL) + + +/* + * Clamp a computed probability estimate (which may suffer from roundoff or + * estimation errors) to valid range. Argument must be a float variable. + */ +#define CLAMP_PROBABILITY(p) \ + do { \ + if (p < 0.0) \ + p = 0.0; \ + else if (p > 1.0) \ + p = 1.0; \ + } while (0) + + typedef enum { Pattern_Type_Like, Pattern_Type_Like_IC, |