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/*------------------------------------------------------------------------
*
* geqo_eval.c
* Routines to evaluate query trees
*
* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: geqo_eval.c,v 1.53 2000/07/28 02:13:16 tgl Exp $
*
*-------------------------------------------------------------------------
*/
/* contributed by:
=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
* Martin Utesch * Institute of Automatic Control *
= = University of Mining and Technology =
* utesch@aut.tu-freiberg.de * Freiberg, Germany *
=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
*/
#include "postgres.h"
#include <math.h>
#include <limits.h>
#include "optimizer/geqo.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "utils/memutils.h"
/*
* geqo_eval
*
* Returns cost of a query tree as an individual of the population.
*/
Cost
geqo_eval(Query *root, Gene *tour, int num_gene)
{
MemoryContext mycontext;
MemoryContext oldcxt;
RelOptInfo *joinrel;
Cost fitness;
List *savelist;
/*
* Create a private memory context that will hold all temp storage
* allocated inside gimme_tree().
*
* Since geqo_eval() will be called many times, we can't afford to let
* all that memory go unreclaimed until end of statement. Note we make
* the temp context a child of TransactionCommandContext, so that
* it will be freed even if we abort via elog(ERROR).
*/
mycontext = AllocSetContextCreate(TransactionCommandContext,
"GEQO",
ALLOCSET_DEFAULT_MINSIZE,
ALLOCSET_DEFAULT_INITSIZE,
ALLOCSET_DEFAULT_MAXSIZE);
oldcxt = MemoryContextSwitchTo(mycontext);
/* preserve root->join_rel_list, which gimme_tree changes */
savelist = root->join_rel_list;
/* construct the best path for the given combination of relations */
joinrel = gimme_tree(root, tour, 0, num_gene, NULL);
/*
* compute fitness
*
* XXX geqo does not currently support optimization for partial result
* retrieval --- how to fix?
*/
fitness = joinrel->cheapest_total_path->total_cost;
/* restore join_rel_list */
root->join_rel_list = savelist;
/* release all the memory acquired within gimme_tree */
MemoryContextSwitchTo(oldcxt);
MemoryContextDelete(mycontext);
return fitness;
}
/*
* gimme_tree
* this program presumes that only LEFT-SIDED TREES are considered!
*
* 'old_rel' is the preceding join
*
* Returns a new join relation incorporating all joins in a left-sided tree.
*/
RelOptInfo *
gimme_tree(Query *root, Gene *tour, int rel_count, int num_gene, RelOptInfo *old_rel)
{
RelOptInfo *inner_rel; /* current relation */
int base_rel_index;
RelOptInfo *new_rel;
if (rel_count < num_gene)
{ /* tree not yet finished */
/* tour[0] = 3; tour[1] = 1; tour[2] = 2 */
base_rel_index = (int) tour[rel_count];
inner_rel = (RelOptInfo *) nth(base_rel_index - 1, root->base_rel_list);
if (rel_count == 0)
{ /* processing first join with
* base_rel_index = (int) tour[0] */
rel_count++;
return gimme_tree(root, tour, rel_count, num_gene, inner_rel);
}
else
{ /* tree main part */
List *acceptable_rels = lcons(inner_rel, NIL);
new_rel = make_rels_by_clause_joins(root, old_rel,
acceptable_rels);
if (!new_rel)
{
new_rel = make_rels_by_clauseless_joins(root, old_rel,
acceptable_rels);
if (!new_rel)
elog(ERROR, "gimme_tree: failed to construct join rel");
}
rel_count++;
Assert(length(new_rel->relids) == rel_count);
/* Find and save the cheapest paths for this rel */
set_cheapest(new_rel);
return gimme_tree(root, tour, rel_count, num_gene, new_rel);
}
}
return old_rel; /* tree finished ... */
}
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