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/*------------------------------------------------------------------------
*
* geqo_eval.c
* Routines to evaluate query trees
*
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: geqo_eval.c,v 1.58 2001/03/22 03:59:33 momjian 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, List *initial_rels, 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, initial_rels, tour, num_gene, 0, 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 routine considers only LEFT-SIDED TREES!
*
* 'root' is the Query
* 'initial_rels' is the list of initial relations (FROM-list items)
* 'tour' is the proposed join order, of length 'num_gene'
* 'rel_count' is number of initial_rels items already joined (initially 0)
* 'old_rel' is the preceding join (initially NULL)
*
* Returns a new join relation incorporating all joins in a left-sided tree.
*/
RelOptInfo *
gimme_tree(Query *root, List *initial_rels,
Gene *tour, int num_gene,
int rel_count, RelOptInfo *old_rel)
{
RelOptInfo *inner_rel; /* current relation */
int init_rel_index;
if (rel_count < num_gene)
{
/* tree not yet finished */
init_rel_index = (int) tour[rel_count];
inner_rel = (RelOptInfo *) nth(init_rel_index - 1, initial_rels);
if (rel_count == 0)
{
/* processing first join with init_rel_index = (int) tour[0] */
rel_count++;
return gimme_tree(root, initial_rels,
tour, num_gene,
rel_count, inner_rel);
}
else
{
/* tree main part */
List *acceptable_rels = makeList1(inner_rel);
List *new_rels;
RelOptInfo *new_rel;
new_rels = make_rels_by_clause_joins(root, old_rel,
acceptable_rels);
/* Shouldn't get more than one result */
Assert(length(new_rels) <= 1);
if (new_rels == NIL)
{
new_rels = make_rels_by_clauseless_joins(root, old_rel,
acceptable_rels);
Assert(length(new_rels) <= 1);
if (new_rels == NIL)
elog(ERROR, "gimme_tree: failed to construct join rel");
}
new_rel = (RelOptInfo *) lfirst(new_rels);
/* Find and save the cheapest paths for this rel */
set_cheapest(new_rel);
/* and recurse... */
rel_count++;
return gimme_tree(root, initial_rels,
tour, num_gene,
rel_count, new_rel);
}
}
return old_rel; /* tree finished ... */
}
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