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Fix range-query estimation to not double-exclude NULLs, per gripe from

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Ray Ontko 28-June-02.  Also, fix prefix_selectivity for NAME lefthand
variables (it was bogusly assuming binary compatibility), and adjust
make_greater_string() to not call pg_mbcliplen() with invalid multibyte
data (this last per bug report that I can't find at the moment, but it
was in July '02).
This commit is contained in:
Tom Lane
2002-10-19 02:56:16 +00:00
parent a3cb8746d9
commit c0f7dcdac1
3 changed files with 49 additions and 36 deletions
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19
src/backend/optimizer/path/clausesel.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/clausesel.c,v 1.51 2002/06/20 20:29:29 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/clausesel.c,v 1.52 2002/10/19 02:56:16 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -102,7 +102,9 @@ restrictlist_selectivity(Query *root,
* see that hisel is the fraction of the range below the high bound, while
* losel is the fraction above the low bound; so hisel can be interpreted
* directly as a 0..1 value but we need to convert losel to 1-losel before
* interpreting it as a value. Then the available range is 1-losel to hisel.)
* 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.
@@ -199,6 +201,9 @@ clauselist_selectivity(Query *root,
/* 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);
/*
* A zero or slightly negative s2 should be converted into a
* small positive value; we probably are dealing with a very
@@ -503,12 +508,18 @@ clause_selectivity(Query *root,
else if (IsA(clause, NullTest))
{
/* Use node specific selectivity calculation function */
s1 = nulltestsel(root, (NullTest *) clause, varRelid);
s1 = nulltestsel(root,
((NullTest *) clause)->nulltesttype,
((NullTest *) clause)->arg,
varRelid);
}
else if (IsA(clause, BooleanTest))
{
/* Use node specific selectivity calculation function */
s1 = booltestsel(root, (BooleanTest *) clause, varRelid);
s1 = booltestsel(root,
((BooleanTest *) clause)->booltesttype,
((BooleanTest *) clause)->arg,
varRelid);
}
else if (IsA(clause, RelabelType))
{