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Change GEQO optimizer to release memory after each gene

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is evaluated.  This bounds memory usage to something reasonable even
when many tables are being joined.
This commit is contained in:
Tom Lane
1999-05-17 00:25:34 +00:00
parent c686be8d56
commit 1332c1e144
4 changed files with 89 additions and 54 deletions
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60
src/backend/optimizer/geqo/geqo_eval.c
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@@ -5,7 +5,7 @@
*
* Copyright (c) 1994, Regents of the University of California
*
* $Id: geqo_eval.c,v 1.36 1999/05/16 19:45:00 tgl Exp $
* $Id: geqo_eval.c,v 1.37 1999/05/17 00:25:34 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -36,6 +36,7 @@
#include "utils/palloc.h"
#include "utils/elog.h"
#include "utils/portal.h"
#include "optimizer/internal.h"
#include "optimizer/paths.h"
@@ -48,6 +49,38 @@
#include "optimizer/geqo_gene.h"
#include "optimizer/geqo.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
*
@@ -56,23 +89,30 @@
Cost
geqo_eval(Query *root, Gene *tour, int num_gene)
{
RelOptInfo *joinrel;
Cost fitness;
List *temp;
MemoryContext oldcxt;
RelOptInfo *joinrel;
Cost fitness;
List *savelist;
/* remember root->join_rel_list ... */
/* because root->join_rel_list will be changed during the following */
temp = listCopy(root->join_rel_list);
/* preserve root->join_rel_list, which gimme_tree changes */
savelist = root->join_rel_list;
/* joinrel is readily processed query tree -- left-sided ! */
/* 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 = (Cost) joinrel->cheapestpath->path_cost;
root->join_rel_list = temp;
/* restore join_rel_list */
root->join_rel_list = savelist;
pfree(joinrel);
/* release all the memory acquired within gimme_tree */
EndPortalAllocMode();
MemoryContextSwitchTo(oldcxt);
return fitness;
}