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Fix oversight in planning for multiple indexscans driven by

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ScalarArrayOpExpr index quals: we were estimating the right total
number of rows returned, but treating the index-access part of the
cost as if a single scan were fetching that many consecutive index
tuples.  Actually we should treat it as a multiple indexscan, and
if there are enough of 'em the Mackert-Lohman discount should kick in.
This commit is contained in:
Tom Lane
2006-07-01 22:07:23 +00:00
parent cffd89ca73
commit 08ccdf020e
3 changed files with 84 additions and 39 deletions
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31
src/backend/optimizer/path/costsize.c
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@ -54,7 +54,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.159 2006/07/01 18:38:32 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.160 2006/07/01 22:07:23 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -112,7 +112,6 @@ bool enable_hashjoin = true;
static bool cost_qual_eval_walker(Node *node, QualCost *total);
static int estimate_array_length(Node *arrayexpr);
static Selectivity approx_selectivity(PlannerInfo *root, List *quals,
JoinType jointype);
static Selectivity join_in_selectivity(JoinPath *path, PlannerInfo *root);
@ -691,34 +690,6 @@ cost_tidscan(Path *path, PlannerInfo *root,
path->total_cost = startup_cost + run_cost;
}
/*
* Estimate number of elements in the array yielded by an expression.
*/
static int
estimate_array_length(Node *arrayexpr)
{
if (arrayexpr && IsA(arrayexpr, Const))
{
Datum arraydatum = ((Const *) arrayexpr)->constvalue;
bool arrayisnull = ((Const *) arrayexpr)->constisnull;
ArrayType *arrayval;
if (arrayisnull)
return 0;
arrayval = DatumGetArrayTypeP(arraydatum);
return ArrayGetNItems(ARR_NDIM(arrayval), ARR_DIMS(arrayval));
}
else if (arrayexpr && IsA(arrayexpr, ArrayExpr))
{
return list_length(((ArrayExpr *) arrayexpr)->elements);
}
else
{
/* default guess */
return 10;
}
}
/*
* cost_subqueryscan
* Determines and returns the cost of scanning a subquery RTE.