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Add selectivity-calculation code for RowCompareExpr nodes. Simplistic,

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but a lot better than nothing at all ...
This commit is contained in:
Tom Lane
2006-01-14 00:14:12 +00:00
parent 39fc1fb07a
commit 34f8ee9737
3 changed files with 73 additions and 3 deletions
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61
src/backend/utils/adt/selfuncs.c
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@ -15,7 +15,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.195 2006/01/10 17:35:52 tgl Exp $
* $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.196 2006/01/14 00:14:11 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -1566,6 +1566,65 @@ scalararraysel(PlannerInfo *root,
return s1;
}
/*
* rowcomparesel - Selectivity of RowCompareExpr Node.
*
* We estimate RowCompare selectivity by considering just the first (high
* order) columns, which makes it equivalent to an ordinary OpExpr. While
* this estimate could be refined by considering additional columns, it
* seems unlikely that we could do a lot better without multi-column
* statistics.
*/
Selectivity
rowcomparesel(PlannerInfo *root,
RowCompareExpr *clause,
int varRelid, JoinType jointype)
{
Selectivity s1;
Oid opno = linitial_oid(clause->opnos);
List *opargs;
bool is_join_clause;
/* Build equivalent arg list for single operator */
opargs = list_make2(linitial(clause->largs), linitial(clause->rargs));
/* Decide if it's a join clause, same as for OpExpr */
if (varRelid != 0)
{
/*
* If we are considering a nestloop join then all clauses are
* restriction clauses, since we are only interested in the one
* relation.
*/
is_join_clause = false;
}
else
{
/*
* Otherwise, it's a join if there's more than one relation used.
* Notice we ignore the low-order columns here.
*/
is_join_clause = (NumRelids((Node *) opargs) > 1);
}
if (is_join_clause)
{
/* Estimate selectivity for a join clause. */
s1 = join_selectivity(root, opno,
opargs,
jointype);
}
else
{
/* Estimate selectivity for a restriction clause. */
s1 = restriction_selectivity(root, opno,
opargs,
varRelid);
}
return s1;
}
/*
* eqjoinsel - Join selectivity of "="
*/