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/*-------------------------------------------------------------------------
*
* geqo_paths.c--
* Routines to process redundant paths and relations
*
* Copyright (c) 1994, Regents of the University of California
*
* $Id: geqo_paths.c,v 1.8 1998/02/26 04:32:23 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "nodes/pg_list.h"
#include "nodes/relation.h"
#include "nodes/primnodes.h"
#include "utils/palloc.h"
#include "utils/elog.h"
#include "optimizer/internal.h"
#include "optimizer/paths.h"
#include "optimizer/pathnode.h"
#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/geqo_paths.h"
static List *geqo_prune_rel(Rel *rel, List *other_rels);
static Path *set_paths(Rel *rel, Path *unorderedpath);
/*
* geqo-prune-rels--
* Removes any redundant relation entries from a list of rel nodes
* 'rel-list'.
*
* Returns the resulting list.
*
*/
List *
geqo_prune_rels(List *rel_list)
{
List *temp_list = NIL;
if (rel_list != NIL)
{
temp_list = lcons(lfirst(rel_list),
geqo_prune_rels(geqo_prune_rel((Rel *) lfirst(rel_list),
lnext(rel_list))));
}
return (temp_list);
}
/*
* geqo-prune-rel--
* Prunes those relations from 'other-rels' that are redundant with
* 'rel'. A relation is redundant if it is built up of the same
* relations as 'rel'. Paths for the redundant relation are merged into
* the pathlist of 'rel'.
*
* Returns a list of non-redundant relations, and sets the pathlist field
* of 'rel' appropriately.
*
*/
static List *
geqo_prune_rel(Rel *rel, List *other_rels)
{
List *i = NIL;
List *t_list = NIL;
List *temp_node = NIL;
Rel *other_rel = (Rel *) NULL;
foreach(i, other_rels)
{
other_rel = (Rel *) lfirst(i);
if (same(rel->relids, other_rel->relids))
{
rel->pathlist = add_pathlist(rel,
rel->pathlist,
other_rel->pathlist);
t_list = nconc(t_list, NIL); /* XXX is this right ? */
}
else
{
temp_node = lcons(other_rel, NIL);
t_list = nconc(t_list, temp_node);
}
}
return (t_list);
}
/*
* geqo-rel-paths--
* For a relation 'rel' (which corresponds to a join
* relation), set pointers to the unordered path and cheapest paths
* (if the unordered path isn't the cheapest, it is pruned), and
* reset the relation's size field to reflect the join.
*
* Returns nothing of interest.
*
*/
void
geqo_rel_paths(Rel *rel)
{
List *y = NIL;
Path *path = (Path *) NULL;
JoinPath *cheapest = (JoinPath *) NULL;
rel->size = 0;
foreach(y, rel->pathlist)
{
path = (Path *) lfirst(y);
if (!path->p_ordering.ord.sortop)
break;
}
cheapest = (JoinPath *) set_paths(rel, path);
if (IsA_JoinPath(cheapest))
rel->size = compute_joinrel_size(cheapest);
}
/*
* set-path--
* Compares the unordered path for a relation with the cheapest path. If
* the unordered path is not cheapest, it is pruned.
*
* Resets the pointers in 'rel' for unordered and cheapest paths.
*
* Returns the cheapest path.
*
*/
static Path *
set_paths(Rel *rel, Path *unorderedpath)
{
Path *cheapest = set_cheapest(rel, rel->pathlist);
/* don't prune if not pruneable -- JMH, 11/23/92 */
if (unorderedpath != cheapest
&& rel->pruneable)
{
rel->unorderedpath = (Path *) NULL;
rel->pathlist = lremove(unorderedpath, rel->pathlist);
}
else
{
rel->unorderedpath = (Path *) unorderedpath;
}
return (cheapest);
}
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