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/*------------------------------------------------------------------------
*
* geqo_eval.c
* Routines to evaluate query trees
*
* Copyright (c) 1994, Regents of the University of California
*
* $Id: geqo_eval.c,v 1.45 2000/01/09 00:26:27 tgl Exp $
*
*-------------------------------------------------------------------------
*/
/* contributed by:
=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
* Martin Utesch * Institute of Automatic Control *
= = University of Mining and Technology =
* utesch@aut.tu-freiberg.de * Freiberg, Germany *
=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
*/
#include <math.h>
#include "postgres.h"
#ifdef HAVE_LIMITS_H
#include <limits.h>
#else
#ifdef HAVE_VALUES_H
#include <values.h>
#endif
#endif
#include "optimizer/cost.h"
#include "optimizer/geqo.h"
#include "optimizer/paths.h"
#include "utils/portal.h"
/*
* Variables set by geqo_eval_startup for use within a single GEQO run
*/
static MemoryContext geqo_eval_context;
/*
* geqo_eval_startup:
* Must be called during geqo_main startup (before geqo_eval may be called)
*
* The main thing we need to do here is prepare a private memory context for
* allocation of temp storage used while constructing a path in geqo_eval().
* Since geqo_eval() will be called many times, we can't afford to let all
* that memory go unreclaimed until end of statement. We use a special
* named portal to hold the context, so that it will be freed even if
* we abort via elog(ERROR). The working data is allocated in the portal's
* heap memory context.
*/
void
geqo_eval_startup(void)
{
#define GEQO_PORTAL_NAME "<geqo workspace>"
Portal geqo_portal = GetPortalByName(GEQO_PORTAL_NAME);
if (!PortalIsValid(geqo_portal))
{
/* First time through (within current transaction, that is) */
geqo_portal = CreatePortal(GEQO_PORTAL_NAME);
Assert(PortalIsValid(geqo_portal));
}
geqo_eval_context = (MemoryContext) PortalGetHeapMemory(geqo_portal);
}
/*
* 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 oldcxt;
RelOptInfo *joinrel;
Cost fitness;
List *savelist;
/* preserve root->join_rel_list, which gimme_tree changes */
savelist = root->join_rel_list;
/*
* create a temporary allocation context for the path construction
* work
*/
oldcxt = MemoryContextSwitchTo(geqo_eval_context);
StartPortalAllocMode(DefaultAllocMode, 0);
/* construct the best path for the given combination of relations */
joinrel = gimme_tree(root, tour, 0, num_gene, NULL);
/* compute fitness */
fitness = joinrel->cheapestpath->path_cost;
/* restore join_rel_list */
root->join_rel_list = savelist;
/* release all the memory acquired within gimme_tree */
EndPortalAllocMode();
MemoryContextSwitchTo(oldcxt);
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;
List *new_rels;
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 */
if (!(new_rels = make_rels_by_clause_joins(root, old_rel,
old_rel->joininfo,
inner_rel->relids)))
{
new_rels = make_rels_by_clauseless_joins(old_rel,
lcons(inner_rel, NIL));
/*
* we don't do bushy plans in geqo, do we? bjm 02/18/1999
* new_rels = append(new_rels,
* make_rels_by_clauseless_joins(old_rel,
* lcons(old_rel,NIL));
*/
}
/* process new_rel->pathlist */
update_rels_pathlist_for_joins(root, new_rels);
/* prune new_rels */
/* MAU: is this necessary? */
/*
* what's the matter if more than one new rel is left till
* now?
*/
/*
* joinrels in newrels with different ordering of relids are
* not possible
*/
if (length(new_rels) > 1)
merge_rels_with_same_relids(new_rels);
if (length(new_rels) > 1)
{ /* should never be reached ... */
elog(DEBUG, "gimme_tree: still %d relations left", length(new_rels));
}
rels_set_cheapest(root, new_rels);
/* get essential new relation */
new_rel = (RelOptInfo *) lfirst(new_rels);
rel_count++;
/* processing of other new_rel attributes */
set_rel_rows_width(root, new_rel);
root->join_rel_list = lcons(new_rel, NIL);
return gimme_tree(root, tour, rel_count, num_gene, new_rel);
}
}
return old_rel; /* tree finished ... */
}
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