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554 lines
16 KiB
C
554 lines
16 KiB
C
/*-------------------------------------------------------------------------
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*
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* joinpath.c
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* Routines to find all possible paths for processing a set of joins
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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/joinpath.c,v 1.39 1999/07/15 22:39:24 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include <sys/types.h>
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#include <math.h>
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#include "postgres.h"
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#include "optimizer/paths.h"
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#include "optimizer/pathnode.h"
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#include "optimizer/cost.h" /* for _enable_{hashjoin,
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* _enable_mergejoin} */
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static Path *best_innerjoin(List *join_paths, List *outer_relid);
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static List *sort_inner_and_outer(RelOptInfo *joinrel, RelOptInfo *outerrel, RelOptInfo *innerrel,
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List *mergeinfo_list);
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static List *match_unsorted_outer(RelOptInfo *joinrel, RelOptInfo *outerrel, RelOptInfo *innerrel,
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List *outerpath_list, Path *cheapest_inner, Path *best_innerjoin,
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List *mergeinfo_list);
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static List *match_unsorted_inner(RelOptInfo *joinrel, RelOptInfo *outerrel, RelOptInfo *innerrel,
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List *innerpath_list, List *mergeinfo_list);
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static List *hash_inner_and_outer(RelOptInfo *joinrel, RelOptInfo *outerrel, RelOptInfo *innerrel,
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List *hashinfo_list);
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/*
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* update_rels_pathlist_for_joins
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* Creates all possible ways to process joins for each of the join
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* relations in the list 'joinrels.' Each unique path will be included
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* in the join relation's 'pathlist' field.
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*
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* In postgres, n-way joins are handled left-only(permuting clauseless
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* joins doesn't usually win much).
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*
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* if BushyPlanFlag is true, bushy tree plans will be generated
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*
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* 'joinrels' is the list of relation entries to be joined
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*
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* Modifies the pathlist field of the appropriate rel node to contain
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* the unique join paths.
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* If bushy trees are considered, may modify the relid field of the
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* join rel nodes to flatten the lists.
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*
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* It does a destructive modification.
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*/
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void
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update_rels_pathlist_for_joins(Query *root, List *joinrels)
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{
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List *mergeinfo_list = NIL;
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List *hashinfo_list = NIL;
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List *j;
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foreach(j, joinrels)
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{
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RelOptInfo *joinrel = (RelOptInfo *) lfirst(j);
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Relids innerrelids;
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Relids outerrelids;
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RelOptInfo *innerrel;
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RelOptInfo *outerrel;
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Path *bestinnerjoin;
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List *pathlist = NIL;
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/* flatten out relids later in this function */
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outerrelids = lfirst(joinrel->relids);
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innerrelids = lsecond(joinrel->relids);
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/*
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* base relation id is an integer and join relation relid is a
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* list of integers.
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*/
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innerrel = (length(innerrelids) == 1) ?
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get_base_rel(root, lfirsti(innerrelids)) :
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get_join_rel(root, innerrelids);
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outerrel = (length(outerrelids) == 1) ?
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get_base_rel(root, lfirsti(outerrelids)) :
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get_join_rel(root, outerrelids);
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bestinnerjoin = best_innerjoin(innerrel->innerjoin, outerrel->relids);
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if (_enable_mergejoin_)
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mergeinfo_list = group_clauses_by_order(joinrel->restrictinfo,
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innerrel->relids);
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if (_enable_hashjoin_)
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hashinfo_list = group_clauses_by_hashop(joinrel->restrictinfo,
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innerrel->relids);
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/* need to flatten the relids list */
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joinrel->relids = nconc(listCopy(outerrelids),
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listCopy(innerrelids));
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/*
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* 1. Consider mergejoin paths where both relations must be
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* explicitly sorted.
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*/
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pathlist = sort_inner_and_outer(joinrel, outerrel,
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innerrel, mergeinfo_list);
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/*
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* 2. Consider paths where the outer relation need not be
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* explicitly sorted. This may include either nestloops and
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* mergejoins where the outer path is already ordered.
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*/
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pathlist = add_pathlist(joinrel, pathlist,
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match_unsorted_outer(joinrel,
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outerrel,
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innerrel,
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outerrel->pathlist,
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innerrel->cheapestpath,
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bestinnerjoin,
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mergeinfo_list));
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/*
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* 3. Consider paths where the inner relation need not be
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* explicitly sorted. This may include nestloops and mergejoins
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* the actual nestloop nodes were constructed in
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* (match_unsorted_outer).
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*/
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pathlist = add_pathlist(joinrel, pathlist,
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match_unsorted_inner(joinrel, outerrel,
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innerrel,
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innerrel->pathlist,
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mergeinfo_list));
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/*
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* 4. Consider paths where both outer and inner relations must be
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* hashed before being joined.
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*/
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pathlist = add_pathlist(joinrel, pathlist,
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hash_inner_and_outer(joinrel, outerrel,
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innerrel, hashinfo_list));
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joinrel->pathlist = pathlist;
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}
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}
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/*
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* best_innerjoin
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* Find the cheapest index path that has already been identified by
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* (indexable_joinclauses) as being a possible inner path for the given
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* outer relation in a nestloop join.
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*
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* 'join_paths' is a list of join nodes
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* 'outer_relid' is the relid of the outer join relation
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*
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* Returns the pathnode of the selected path.
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*/
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static Path *
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best_innerjoin(List *join_paths, Relids outer_relids)
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{
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Path *cheapest = (Path *) NULL;
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List *join_path;
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foreach(join_path, join_paths)
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{
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Path *path = (Path *) lfirst(join_path);
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if (intMember(lfirsti(path->joinid), outer_relids) &&
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(cheapest == NULL ||
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path_is_cheaper(path, cheapest)))
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cheapest = path;
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}
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return cheapest;
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}
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/*
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* sort_inner_and_outer
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* Create mergejoin join paths by explicitly sorting both the outer and
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* inner join relations on each available merge ordering.
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*
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* 'joinrel' is the join relation
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* 'outerrel' is the outer join relation
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* 'innerrel' is the inner join relation
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* 'mergeinfo_list' is a list of nodes containing info on(mergejoinable)
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* clauses for joining the relations
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*
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* Returns a list of mergejoin paths.
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*/
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static List *
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sort_inner_and_outer(RelOptInfo *joinrel,
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RelOptInfo *outerrel,
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RelOptInfo *innerrel,
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List *mergeinfo_list)
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{
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List *ms_list = NIL;
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MergeInfo *xmergeinfo = (MergeInfo *) NULL;
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MergePath *temp_node = (MergePath *) NULL;
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List *i;
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List *outerkeys = NIL;
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List *innerkeys = NIL;
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List *merge_pathkeys = NIL;
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foreach(i, mergeinfo_list)
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{
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xmergeinfo = (MergeInfo *) lfirst(i);
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outerkeys = make_pathkeys_from_joinkeys(xmergeinfo->jmethod.jmkeys,
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outerrel->targetlist,
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OUTER);
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innerkeys = make_pathkeys_from_joinkeys(xmergeinfo->jmethod.jmkeys,
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innerrel->targetlist,
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INNER);
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merge_pathkeys = new_join_pathkeys(outerkeys, joinrel->targetlist,
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xmergeinfo->jmethod.clauses);
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temp_node = create_mergejoin_path(joinrel,
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outerrel->size,
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innerrel->size,
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outerrel->width,
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innerrel->width,
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(Path *) outerrel->cheapestpath,
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(Path *) innerrel->cheapestpath,
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merge_pathkeys,
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xmergeinfo->m_ordering,
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xmergeinfo->jmethod.clauses,
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outerkeys,
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innerkeys);
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ms_list = lappend(ms_list, temp_node);
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}
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return ms_list;
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}
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/*
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* match_unsorted_outer
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* Creates possible join paths for processing a single join relation
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* 'joinrel' by employing either iterative substitution or
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* mergejoining on each of its possible outer paths(assuming that the
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* outer relation need not be explicitly sorted).
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*
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* 1. The inner path is the cheapest available inner path.
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* 2. Mergejoin wherever possible. Mergejoin are considered if there
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* are mergejoinable join clauses between the outer and inner join
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* relations such that the outer path is keyed on the variables
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* appearing in the clauses. The corresponding inner merge path is
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* either a path whose keys match those of the outer path(if such a
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* path is available) or an explicit sort on the appropriate inner
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* join keys, whichever is cheaper.
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*
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* 'joinrel' is the join relation
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* 'outerrel' is the outer join relation
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* 'innerrel' is the inner join relation
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* 'outerpath_list' is the list of possible outer paths
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* 'cheapest_inner' is the cheapest inner path
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* 'best_innerjoin' is the best inner index path(if any)
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* 'mergeinfo_list' is a list of nodes containing info on mergejoinable
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* clauses
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*
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* Returns a list of possible join path nodes.
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*/
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static List *
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match_unsorted_outer(RelOptInfo *joinrel,
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RelOptInfo *outerrel,
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RelOptInfo *innerrel,
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List *outerpath_list,
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Path *cheapest_inner,
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Path *best_innerjoin,
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List *mergeinfo_list)
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{
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Path *outerpath = (Path *) NULL;
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List *jp_list = NIL;
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List *temp_node = NIL;
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List *merge_pathkeys = NIL;
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Path *nestinnerpath = (Path *) NULL;
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List *paths = NIL;
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List *i = NIL;
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PathOrder *outerpath_ordering = NULL;
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foreach(i, outerpath_list)
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{
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List *clauses = NIL;
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List *matchedJoinKeys = NIL;
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List *matchedJoinClauses = NIL;
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MergeInfo *xmergeinfo = NULL;
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outerpath = (Path *) lfirst(i);
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outerpath_ordering = outerpath->pathorder;
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if (outerpath_ordering)
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xmergeinfo = match_order_mergeinfo(outerpath_ordering,
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mergeinfo_list);
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if (xmergeinfo)
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clauses = xmergeinfo->jmethod.clauses;
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if (clauses)
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{
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List *jmkeys = xmergeinfo->jmethod.jmkeys;
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order_joinkeys_by_pathkeys(outerpath->pathkeys,
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jmkeys,
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clauses,
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OUTER,
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&matchedJoinKeys,
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&matchedJoinClauses);
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merge_pathkeys = new_join_pathkeys(outerpath->pathkeys,
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joinrel->targetlist, clauses);
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}
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else
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merge_pathkeys = outerpath->pathkeys;
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if (best_innerjoin &&
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path_is_cheaper(best_innerjoin, cheapest_inner))
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nestinnerpath = best_innerjoin;
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else
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nestinnerpath = cheapest_inner;
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paths = lcons(create_nestloop_path(joinrel,
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outerrel,
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outerpath,
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nestinnerpath,
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merge_pathkeys),
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NIL);
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if (clauses && matchedJoinKeys)
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{
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bool path_is_cheaper_than_sort;
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List *varkeys = NIL;
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Path *mergeinnerpath = get_cheapest_path_for_joinkeys(
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matchedJoinKeys,
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outerpath_ordering,
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innerrel->pathlist,
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INNER);
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/* Should we use the mergeinner, or sort the cheapest inner? */
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path_is_cheaper_than_sort = (bool) (mergeinnerpath &&
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(mergeinnerpath->path_cost <
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(cheapest_inner->path_cost +
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cost_sort(matchedJoinKeys, innerrel->size,
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innerrel->width))));
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if (!path_is_cheaper_than_sort)
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{
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varkeys = make_pathkeys_from_joinkeys(matchedJoinKeys,
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innerrel->targetlist,
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INNER);
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}
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/*
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* Keep track of the cost of the outer path used with this
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* ordered inner path for later processing in
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* (match_unsorted_inner), since it isn't a sort and thus
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* wouldn't otherwise be considered.
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*/
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if (path_is_cheaper_than_sort)
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mergeinnerpath->outerjoincost = outerpath->path_cost;
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else
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mergeinnerpath = cheapest_inner;
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temp_node = lcons(create_mergejoin_path(joinrel,
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outerrel->size,
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innerrel->size,
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outerrel->width,
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innerrel->width,
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outerpath,
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mergeinnerpath,
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merge_pathkeys,
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xmergeinfo->m_ordering,
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matchedJoinClauses,
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NIL,
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varkeys),
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paths);
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}
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else
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temp_node = paths;
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jp_list = nconc(jp_list, temp_node);
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}
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return jp_list;
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}
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/*
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* match_unsorted_inner
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* Find the cheapest ordered join path for a given(ordered, unsorted)
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* inner join path.
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*
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* Scans through each path available on an inner join relation and tries
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* matching its ordering keys against those of mergejoin clauses.
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* If 1. an appropriately_ordered inner path and matching mergeclause are
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* found, and
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* 2. sorting the cheapest outer path is cheaper than using an ordered
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* but unsorted outer path(as was considered in
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* (match_unsorted_outer)), then this merge path is considered.
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*
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* 'joinrel' is the join result relation
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* 'outerrel' is the outer join relation
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* 'innerrel' is the inner join relation
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* 'innerpath_list' is the list of possible inner join paths
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* 'mergeinfo_list' is a list of nodes containing info on mergejoinable
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* clauses
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*
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* Returns a list of possible merge paths.
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*/
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static List *
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match_unsorted_inner(RelOptInfo *joinrel,
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RelOptInfo *outerrel,
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RelOptInfo *innerrel,
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List *innerpath_list,
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List *mergeinfo_list)
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{
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List *mp_list = NIL;
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List *i;
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foreach(i, innerpath_list)
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{
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Path *innerpath = (Path *) lfirst(i);
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PathOrder *innerpath_ordering = innerpath->pathorder;
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MergeInfo *xmergeinfo = (MergeInfo *) NULL;
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List *clauses = NIL;
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List *matchedJoinKeys = NIL;
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List *matchedJoinClauses = NIL;
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if (innerpath_ordering)
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xmergeinfo = match_order_mergeinfo(innerpath_ordering,
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mergeinfo_list);
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if (xmergeinfo)
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clauses = ((JoinMethod *) xmergeinfo)->clauses;
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if (clauses)
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{
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List *jmkeys = xmergeinfo->jmethod.jmkeys;
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order_joinkeys_by_pathkeys(innerpath->pathkeys,
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jmkeys,
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clauses,
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INNER,
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&matchedJoinKeys,
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&matchedJoinClauses);
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}
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/*
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* (match_unsorted_outer) if it is applicable. 'OuterJoinCost was
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* set above in
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*/
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if (clauses && matchedJoinKeys)
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{
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Cost temp1;
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temp1 = outerrel->cheapestpath->path_cost +
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cost_sort(matchedJoinKeys, outerrel->size, outerrel->width);
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if (innerpath->outerjoincost <= 0 /* unset? */
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|| innerpath->outerjoincost > temp1)
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{
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List *outerkeys = make_pathkeys_from_joinkeys(matchedJoinKeys,
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outerrel->targetlist,
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OUTER);
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List *merge_pathkeys = new_join_pathkeys(outerkeys,
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joinrel->targetlist,
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clauses);
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mp_list = lappend(mp_list,
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create_mergejoin_path(joinrel,
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outerrel->size,
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innerrel->size,
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outerrel->width,
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innerrel->width,
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(Path *) outerrel->cheapestpath,
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innerpath,
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merge_pathkeys,
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xmergeinfo->m_ordering,
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matchedJoinClauses,
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outerkeys,
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NIL));
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}
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}
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}
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return mp_list;
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}
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/*
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* hash_inner_and_outer-- XXX HASH
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* Create hashjoin join paths by explicitly hashing both the outer and
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* inner join relations on each available hash op.
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*
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* 'joinrel' is the join relation
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* 'outerrel' is the outer join relation
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* 'innerrel' is the inner join relation
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* 'hashinfo_list' is a list of nodes containing info on(hashjoinable)
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* clauses for joining the relations
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*
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* Returns a list of hashjoin paths.
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*/
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static List *
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hash_inner_and_outer(RelOptInfo *joinrel,
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RelOptInfo *outerrel,
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RelOptInfo *innerrel,
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List *hashinfo_list)
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{
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List *hjoin_list = NIL;
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List *i;
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foreach(i, hashinfo_list)
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{
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HashInfo *xhashinfo = (HashInfo *) lfirst(i);
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List *outerkeys;
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List *innerkeys;
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List *hash_pathkeys;
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HashPath *temp_node;
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outerkeys = make_pathkeys_from_joinkeys(
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((JoinMethod *) xhashinfo)->jmkeys,
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outerrel->targetlist,
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OUTER);
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innerkeys = make_pathkeys_from_joinkeys(
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((JoinMethod *) xhashinfo)->jmkeys,
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innerrel->targetlist,
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INNER);
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/*
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* We cannot assume that the output of the hashjoin appears in any
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* particular order, so it should have NIL pathkeys.
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*/
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#ifdef NOT_USED
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hash_pathkeys = new_join_pathkeys(outerkeys,
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joinrel->targetlist,
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((JoinMethod *) xhashinfo)->clauses);
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#else
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hash_pathkeys = NIL;
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#endif
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temp_node = create_hashjoin_path(joinrel,
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outerrel->size,
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|
innerrel->size,
|
|
outerrel->width,
|
|
innerrel->width,
|
|
(Path *) outerrel->cheapestpath,
|
|
(Path *) innerrel->cheapestpath,
|
|
hash_pathkeys,
|
|
xhashinfo->hashop,
|
|
((JoinMethod *) xhashinfo)->clauses,
|
|
outerkeys,
|
|
innerkeys);
|
|
hjoin_list = lappend(hjoin_list, temp_node);
|
|
}
|
|
|
|
return hjoin_list;
|
|
}
|