*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/optimizer/path/clausesel.c,v 1.70 2004/08/29 05:06:43 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/path/clausesel.c,v 1.71 2004/11/09 00:34:38 tgl Exp $
*
*-------------------------------------------------------------------------
*/
* interpreting it as a value. Then the available range is 1-losel to hisel.
* However, this calculation double-excludes nulls, so really we need
* hisel + losel + null_frac - 1.)
- * If the calculation yields zero or negative, however, we chicken out and
- * use a default estimate; that probably means that one or both
- * selectivities is a default estimate rather than an actual range value.
+ *
+ * If either selectivity is exactly DEFAULT_INEQ_SEL, we forget this equation
+ * and instead use DEFAULT_RANGE_INEQ_SEL. The same applies if the equation
+ * yields an impossible (negative) result.
*
* A free side-effect is that we can recognize redundant inequalities such
* as "x < 4 AND x < 5"; only the tighter constraint will be counted.
if (rqlist->have_lobound && rqlist->have_hibound)
{
/* Successfully matched a pair of range clauses */
- Selectivity s2 = rqlist->hibound + rqlist->lobound - 1.0;
-
- /* Adjust for double-exclusion of NULLs */
- s2 += nulltestsel(root, IS_NULL, rqlist->var, varRelid);
+ Selectivity s2;
/*
- * A zero or slightly negative s2 should be converted into a
- * small positive value; we probably are dealing with a very
- * tight range and got a bogus result due to roundoff errors.
- * However, if s2 is very negative, then we probably have
- * default selectivity estimates on one or both sides of the
- * range. In that case, insert a not-so-wildly-optimistic
- * default estimate.
+ * Exact equality to the default value probably means the
+ * selectivity function punted. This is not airtight but
+ * should be good enough.
*/
- if (s2 <= 0.0)
+ if (rqlist->hibound == DEFAULT_INEQ_SEL ||
+ rqlist->lobound == DEFAULT_INEQ_SEL)
{
- if (s2 < -0.01)
- {
- /*
- * No data available --- use a default estimate that
- * is small, but not real small.
- */
- s2 = 0.005;
- }
- else
+ s2 = DEFAULT_RANGE_INEQ_SEL;
+ }
+ else
+ {
+ s2 = rqlist->hibound + rqlist->lobound - 1.0;
+
+ /* Adjust for double-exclusion of NULLs */
+ s2 += nulltestsel(root, IS_NULL, rqlist->var, varRelid);
+
+ /*
+ * A zero or slightly negative s2 should be converted into a
+ * small positive value; we probably are dealing with a very
+ * tight range and got a bogus result due to roundoff errors.
+ * However, if s2 is very negative, then we probably have
+ * default selectivity estimates on one or both sides of the
+ * range that we failed to recognize above for some reason.
+ */
+ if (s2 <= 0.0)
{
- /*
- * It's just roundoff error; use a small positive
- * value
- */
- s2 = 1.0e-10;
+ if (s2 < -0.01)
+ {
+ /*
+ * No data available --- use a default estimate that
+ * is small, but not real small.
+ */
+ s2 = DEFAULT_RANGE_INEQ_SEL;
+ }
+ else
+ {
+ /*
+ * It's just roundoff error; use a small positive
+ * value
+ */
+ s2 = 1.0e-10;
+ }
}
}
/* Merge in the selectivity of the pair of clauses */
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.166 2004/09/18 19:39:50 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.167 2004/11/09 00:34:42 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "utils/syscache.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 (1.0 / 3.0)
-
-/* 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)
-
-
/* Return data from examine_variable and friends */
typedef struct
{
* 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 $
*
*-------------------------------------------------------------------------
*/
#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,
projects / thirdparty / postgresql.git / commitdiff
