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Make cost estimates for SubqueryScan more realistic: charge cpu_tuple_cost

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for each row processed, and don't forget the evaluation cost of any
restriction clauses attached to the node.  Per discussion with Greg Stark.
This commit is contained in:
Tom Lane
2003-07-14 22:35:54 +00:00
parent b800196230
commit 3d09f6c560
4 changed files with 53 additions and 9 deletions
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34
src/backend/optimizer/path/costsize.c
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@ -49,7 +49,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.109 2003/06/29 23:05:04 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.110 2003/07/14 22:35:54 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -415,6 +415,38 @@ cost_tidscan(Path *path, Query *root,
path->total_cost = startup_cost + run_cost;
}
/*
* cost_subqueryscan
* Determines and returns the cost of scanning a subquery RTE.
*/
void
cost_subqueryscan(Path *path, RelOptInfo *baserel)
{
Cost startup_cost;
Cost run_cost;
Cost cpu_per_tuple;
/* Should only be applied to base relations that are subqueries */
Assert(baserel->relid > 0);
Assert(baserel->rtekind == RTE_SUBQUERY);
/*
* Cost of path is cost of evaluating the subplan, plus cost of
* evaluating any restriction clauses that will be attached to the
* SubqueryScan node, plus cpu_tuple_cost to account for selection
* and projection overhead.
*/
path->startup_cost = baserel->subplan->startup_cost;
path->total_cost = baserel->subplan->total_cost;
startup_cost = baserel->baserestrictcost.startup;
cpu_per_tuple = cpu_tuple_cost + baserel->baserestrictcost.per_tuple;
run_cost = cpu_per_tuple * baserel->tuples;
path->startup_cost += startup_cost;
path->total_cost += startup_cost + run_cost;
}
/*
* cost_functionscan
* Determines and returns the cost of scanning a function RTE.