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/*-------------------------------------------------------------------------
*
* prune.c--
* Routines to prune redundant paths and relations
*
* Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/Attic/prune.c,v 1.28 1999/02/12 05:56:51 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "nodes/pg_list.h"
#include "nodes/relation.h"
#include "optimizer/internal.h"
#include "optimizer/cost.h"
#include "optimizer/paths.h"
#include "optimizer/pathnode.h"
#include "utils/elog.h"
static List *prune_joinrel(RelOptInfo *rel, List *other_rels);
/*
* prune-joinrels--
* Removes any redundant relation entries from a list of rel nodes
* 'rel-list'. Obviously, the first relation can't be a duplicate.
*
* Returns the resulting list.
*
*/
void
prune_joinrels(List *rel_list)
{
List *i;
/*
* rel_list can shorten while running as duplicate relations are
* deleted
*/
foreach(i, rel_list)
lnext(i) = prune_joinrel((RelOptInfo *) lfirst(i), lnext(i));
}
/*
* prune-joinrel--
* 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 *
prune_joinrel(RelOptInfo *rel, List *other_rels)
{
List *i = NIL;
List *result = NIL;
foreach(i, other_rels)
{
RelOptInfo *other_rel = (RelOptInfo *) lfirst(i);
if (same(rel->relids, other_rel->relids))
/*
* This are on the same relations,
* so get the best of their pathlists.
*/
rel->pathlist = add_pathlist(rel,
rel->pathlist,
other_rel->pathlist);
else
result = lappend(result, other_rel);
}
return result;
}
/*
* rels-set-cheapest
* For each relation entry in 'rel-list' (which corresponds to a join
* relation), set pointers to the cheapest path
*/
void
rels_set_cheapest(List *rel_list)
{
List *x = NIL;
RelOptInfo *rel = (RelOptInfo *) NULL;
JoinPath *cheapest;
foreach(x, rel_list)
{
rel = (RelOptInfo *) lfirst(x);
cheapest = (JoinPath *) set_cheapest(rel, rel->pathlist);
if (IsA_JoinPath(cheapest))
rel->size = compute_joinrel_size(cheapest);
else
elog(ERROR, "non JoinPath called");
}
}
/*
* merge-joinrels--
* Given two lists of rel nodes that are already
* pruned, merge them into one pruned rel node list
*
* 'rel-list1' and
* 'rel-list2' are the rel node lists
*
* Returns one pruned rel node list
*/
List *
merge_joinrels(List *rel_list1, List *rel_list2)
{
List *xrel = NIL;
foreach(xrel, rel_list1)
{
RelOptInfo *rel = (RelOptInfo *) lfirst(xrel);
rel_list2 = prune_joinrel(rel, rel_list2);
}
return append(rel_list1, rel_list2);
}
/*
* prune_oldrels--
* If all the joininfo's in a rel node are inactive,
* that means that this node has been joined into
* other nodes in all possible ways, therefore
* this node can be discarded. If not, it will cause
* extra complexity of the optimizer.
*
* old_rels is a list of rel nodes
*
* Returns a new list of rel nodes
*/
List *
prune_oldrels(List *old_rels)
{
RelOptInfo *rel;
List *joininfo_list,
*xjoininfo,
*i,
*temp_list = NIL;
foreach(i, old_rels)
{
rel = (RelOptInfo *) lfirst(i);
joininfo_list = rel->joininfo;
if (joininfo_list == NIL)
temp_list = lcons(rel, temp_list);
else
{
foreach(xjoininfo, joininfo_list)
{
JoinInfo *joininfo = (JoinInfo *) lfirst(xjoininfo);
if (!joininfo->inactive)
{
temp_list = lcons(rel, temp_list);
break;
}
}
}
}
return temp_list;
}
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