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Fix some bogosities in the code that deals with estimating the fraction

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of tuples we are going to retrieve from a sub-SELECT.  Must have been
half asleep when I did this code the first time :-(
This commit is contained in:
Tom Lane
2000-03-14 02:23:15 +00:00
parent a1642089bf
commit 6217a8c7ba
3 changed files with 42 additions and 29 deletions
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20
src/backend/optimizer/path/costsize.c
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@@ -42,7 +42,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.52 2000/02/15 20:49:16 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.53 2000/03/14 02:23:14 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -687,8 +687,8 @@ cost_qual_eval_walker(Node *node, Cost *total)
* (We assume that sub-selects that can be executed as
* InitPlans have already been removed from the expression.)
*
* NOTE: this logic should agree with make_subplan in
* subselect.c.
* NOTE: this logic should agree with the estimates used by
* make_subplan() in plan/subselect.c.
*/
{
SubPlan *subplan = (SubPlan *) expr->oper;
@@ -701,16 +701,18 @@ cost_qual_eval_walker(Node *node, Cost *total)
subcost = plan->startup_cost +
(plan->total_cost - plan->startup_cost) / plan->plan_rows;
}
else if (subplan->sublink->subLinkType == EXPR_SUBLINK)
{
/* assume we need all tuples */
subcost = plan->total_cost;
}
else
else if (subplan->sublink->subLinkType == ALL_SUBLINK ||
subplan->sublink->subLinkType == ANY_SUBLINK)
{
/* assume we need 50% of the tuples */
subcost = plan->startup_cost +
0.50 * (plan->total_cost - plan->startup_cost);
/* XXX what if subplan has been materialized? */
}
else
{
/* assume we need all tuples */
subcost = plan->total_cost;
}
*total += subcost;
}