e6381966c1
store all ordering information in pathkeys lists (which are now lists of lists of PathKeyItem nodes, not just lists of lists of vars). This was a big win --- the code is smaller and IMHO more understandable than it was, even though it handles more cases. I believe the node changes will not force an initdb for anyone; planner nodes don't show up in stored rules.
109 lines
2.8 KiB
C
109 lines
2.8 KiB
C
/*-------------------------------------------------------------------------
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*
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* prune.c
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* Routines to prune redundant paths and relations
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*
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* Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/optimizer/path/Attic/prune.c,v 1.43 1999/08/16 02:17:52 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "optimizer/cost.h"
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#include "optimizer/pathnode.h"
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#include "optimizer/paths.h"
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static List *merge_rel_with_same_relids(RelOptInfo *rel, List *unmerged_rels);
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/*
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* merge_rels_with_same_relids
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* Removes any redundant relation entries from a list of rel nodes
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* 'rel_list', merging their pathlists into the first non-duplicate
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* relation entry for each value of relids.
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*
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* Returns the resulting list.
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*/
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void
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merge_rels_with_same_relids(List *rel_list)
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{
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List *i;
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/*
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* rel_list can shorten while running as duplicate relations are
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* deleted. Obviously, the first relation can't be a duplicate,
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* so the list head pointer won't change.
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*/
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foreach(i, rel_list)
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{
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lnext(i) = merge_rel_with_same_relids((RelOptInfo *) lfirst(i),
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lnext(i));
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}
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}
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/*
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* merge_rel_with_same_relids
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* Prunes those relations from 'unmerged_rels' that are redundant with
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* 'rel'. A relation is redundant if it is built up of the same
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* relations as 'rel'. Paths for the redundant relations are merged into
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* the pathlist of 'rel'.
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*
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* Returns a list of non-redundant relations, and sets the pathlist field
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* of 'rel' appropriately.
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*
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*/
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static List *
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merge_rel_with_same_relids(RelOptInfo *rel, List *unmerged_rels)
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{
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List *result = NIL;
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List *i;
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foreach(i, unmerged_rels)
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{
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RelOptInfo *unmerged_rel = (RelOptInfo *) lfirst(i);
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if (same(rel->relids, unmerged_rel->relids))
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{
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/*
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* These rels are for the same set of base relations,
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* so get the best of their pathlists. We assume it's
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* ok to reassign a path to the other RelOptInfo without
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* doing more than changing its parent pointer (cf. pathnode.c).
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*/
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rel->pathlist = add_pathlist(rel,
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rel->pathlist,
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unmerged_rel->pathlist);
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}
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else
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result = lappend(result, unmerged_rel);
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}
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return result;
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}
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/*
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* rels_set_cheapest
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* For each relation entry in 'rel_list' (which should contain only join
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* relations), set pointers to the cheapest path and compute rel size.
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*/
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void
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rels_set_cheapest(List *rel_list)
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{
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List *x;
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foreach(x, rel_list)
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{
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RelOptInfo *rel = (RelOptInfo *) lfirst(x);
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JoinPath *cheapest;
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cheapest = (JoinPath *) set_cheapest(rel, rel->pathlist);
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if (IsA_JoinPath(cheapest))
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rel->size = compute_joinrel_size(cheapest);
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else
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elog(ERROR, "rels_set_cheapest: non JoinPath found");
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}
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}
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