464 lines
12 KiB
C
464 lines
12 KiB
C
/*-------------------------------------------------------------------------
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*
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* joinrels.c
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* Routines to determine which relations should be joined
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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/joinrels.c,v 1.32 1999/02/22 06:08:48 momjian 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 "nodes/pg_list.h"
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#include "nodes/relation.h"
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#include "optimizer/internal.h"
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#include "optimizer/cost.h"
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#include "optimizer/paths.h"
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#include "optimizer/tlist.h"
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#include "optimizer/joininfo.h"
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#include "optimizer/pathnode.h"
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static List *new_joininfo_list(List *joininfo_list, Relids join_relids);
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static bool nonoverlap_sets(List *s1, List *s2);
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static bool is_subset(List *s1, List *s2);
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static void set_joinrel_size(RelOptInfo *joinrel, RelOptInfo *outer_rel,
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RelOptInfo *inner_rel, JoinInfo *jinfo);
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/*
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* make_rels_by_joins
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* Find all possible joins for each of the outer join relations in
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* 'outer_rels'. A rel node is created for each possible join relation,
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* and the resulting list of nodes is returned. If at all possible, only
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* those relations for which join clauses exist are considered. If none
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* of these exist for a given relation, all remaining possibilities are
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* considered.
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*
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* Returns a list of rel nodes corresponding to the new join relations.
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*/
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List *
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make_rels_by_joins(Query *root, List *old_rels)
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{
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List *joined_rels = NIL;
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List *join_list = NIL;
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List *r = NIL;
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foreach(r, old_rels)
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{
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RelOptInfo *old_rel = (RelOptInfo *) lfirst(r);
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if (!(joined_rels = make_rels_by_clause_joins(root, old_rel,
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old_rel->joininfo,
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NIL)))
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{
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/*
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* Oops, we have a relation that is not joined to any other
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* relation. Cartesian product time.
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*/
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joined_rels = make_rels_by_clauseless_joins(old_rel,
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root->base_rel_list);
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joined_rels = nconc(joined_rels,
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make_rels_by_clauseless_joins(old_rel,
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old_rels));
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}
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join_list = nconc(join_list, joined_rels);
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}
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return join_list;
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}
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/*
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* make_rels_by_clause_joins
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* Determines whether joins can be performed between an outer relation
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* 'outer_rel' and those relations within 'outer_rel's joininfo nodes
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* (i.e., relations that participate in join clauses that 'outer_rel'
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* participates in). This is possible if all but one of the relations
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* contained within the join clauses of the joininfo node are already
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* contained within 'outer_rel'.
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*
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* 'outer_rel' is the relation entry for the outer relation
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* 'joininfo_list' is a list of join clauses which 'outer_rel'
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* participates in
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*
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* Returns a list of new join relations.
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*/
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List *
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make_rels_by_clause_joins(Query *root, RelOptInfo *old_rel,
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List *joininfo_list, Relids only_relids)
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{
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List *join_list = NIL;
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List *i = NIL;
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foreach(i, joininfo_list)
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{
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JoinInfo *joininfo = (JoinInfo *) lfirst(i);
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RelOptInfo *joined_rel;
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Relids unjoined_relids = joininfo->unjoined_relids;
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if (unjoined_relids != NIL)
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{
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if (length(unjoined_relids) == 1 &&
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(only_relids == NIL ||
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/* geqo only wants certain relids to make new rels */
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intMember(lfirsti(unjoined_relids), only_relids)))
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{
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joined_rel = make_join_rel(old_rel,
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get_base_rel(root,
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lfirsti(unjoined_relids)),
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joininfo);
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join_list = lappend(join_list, joined_rel);
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/* Right-sided plan */
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if (length(old_rel->relids) > 1)
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{
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joined_rel = make_join_rel(
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get_base_rel(root, lfirsti(unjoined_relids)),
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old_rel,
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joininfo);
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join_list = lappend(join_list, joined_rel);
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}
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}
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if (only_relids == NIL) /* no bushy from geqo */
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{
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List *r;
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foreach(r, root->join_rel_list)
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{
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RelOptInfo *join_rel = lfirst(r);
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Assert(length(join_rel->relids) > 1);
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if (is_subset(unjoined_relids, join_rel->relids) &&
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nonoverlap_sets(old_rel->relids, join_rel->relids))
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{
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joined_rel = make_join_rel(old_rel,
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join_rel,
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joininfo);
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join_list = lappend(join_list, joined_rel);
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}
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}
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}
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}
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}
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return join_list;
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}
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/*
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* make_rels_by_clauseless_joins
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* Given an outer relation 'outer_rel' and a list of inner relations
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* 'inner_rels', create a join relation between 'outer_rel' and each
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* member of 'inner_rels' that isn't already included in 'outer_rel'.
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*
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* Returns a list of new join relations.
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*/
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List *
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make_rels_by_clauseless_joins(RelOptInfo *old_rel, List *inner_rels)
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{
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RelOptInfo *inner_rel;
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List *t_list = NIL;
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List *i = NIL;
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foreach(i, inner_rels)
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{
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inner_rel = (RelOptInfo *) lfirst(i);
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if (nonoverlap_sets(inner_rel->relids, old_rel->relids))
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{
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t_list = lappend(t_list,
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make_join_rel(old_rel,
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inner_rel,
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(JoinInfo *) NULL));
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}
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}
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return t_list;
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}
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/*
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* make_join_rel
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* Creates and initializes a new join relation.
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*
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* 'outer_rel' and 'inner_rel' are relation nodes for the relations to be
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* joined
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* 'joininfo' is the joininfo node(join clause) containing both
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* 'outer_rel' and 'inner_rel', if any exists
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*
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* Returns the new join relation node.
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*/
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RelOptInfo *
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make_join_rel(RelOptInfo *outer_rel, RelOptInfo *inner_rel, JoinInfo *joininfo)
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{
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RelOptInfo *joinrel = makeNode(RelOptInfo);
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List *joinrel_joininfo_list = NIL;
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List *new_outer_tlist;
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List *new_inner_tlist;
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/*
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* Create a new tlist by removing irrelevant elements from both tlists
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* of the outer and inner join relations and then merging the results
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* together.
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*/
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new_outer_tlist = new_join_tlist(outer_rel->targetlist, 1);
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new_inner_tlist = new_join_tlist(inner_rel->targetlist,
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length(new_outer_tlist) + 1);
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joinrel->relids = NIL;
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joinrel->indexed = false;
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joinrel->pages = 0;
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joinrel->tuples = 0;
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joinrel->width = 0;
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/* joinrel->targetlist = NIL;*/
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joinrel->pathlist = NIL;
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joinrel->cheapestpath = (Path *) NULL;
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joinrel->pruneable = true;
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joinrel->classlist = NULL;
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joinrel->relam = InvalidOid;
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joinrel->ordering = NULL;
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joinrel->restrictinfo = NIL;
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joinrel->joininfo = NULL;
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joinrel->innerjoin = NIL;
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/*
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* This function uses a trick to pass inner/outer rels as
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* different lists, and then flattens it out later. bjm
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*/
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joinrel->relids = lcons(outer_rel->relids, lcons(inner_rel->relids, NIL));
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new_outer_tlist = nconc(new_outer_tlist, new_inner_tlist);
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joinrel->targetlist = new_outer_tlist;
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if (joininfo)
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joinrel->restrictinfo = joininfo->jinfo_restrictinfo;
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joinrel_joininfo_list = new_joininfo_list(
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nconc(copyObject(outer_rel->joininfo),
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copyObject(inner_rel->joininfo)),
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nconc(listCopy(outer_rel->relids),
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listCopy(inner_rel->relids)));
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joinrel->joininfo = joinrel_joininfo_list;
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set_joinrel_size(joinrel, outer_rel, inner_rel, joininfo);
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return joinrel;
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}
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/*
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* new_join_tlist
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* Builds a join relations's target list by keeping those elements that
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* will be in the final target list and any other elements that are still
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* needed for future joins. For a target list entry to still be needed
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* for future joins, its 'joinlist' field must not be empty after removal
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* of all relids in 'other_relids'.
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*
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* 'tlist' is the target list of one of the join relations
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* 'other_relids' is a list of relids contained within the other
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* join relation
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* 'first_resdomno' is the resdom number to use for the first created
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* target list entry
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*
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* Returns the new target list.
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*/
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List *
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new_join_tlist(List *tlist,
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int first_resdomno)
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{
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int resdomno = first_resdomno - 1;
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TargetEntry *xtl = NULL;
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List *t_list = NIL;
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List *i = NIL;
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List *join_list = NIL;
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bool in_final_tlist = false;
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foreach(i, tlist)
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{
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xtl = lfirst(i);
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/* XXX surely this is wrong? join_list is never changed? tgl 2/99 */
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in_final_tlist = (join_list == NIL);
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if (in_final_tlist)
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{
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resdomno += 1;
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t_list = lappend(t_list,create_tl_element(get_expr(xtl), resdomno));
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}
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}
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return t_list;
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}
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/*
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* new_joininfo_list
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* Builds a join relation's joininfo list by checking for join clauses
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* which still need to used in future joins involving this relation. A
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* join clause is still needed if there are still relations in the clause
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* not contained in the list of relations comprising this join relation.
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* New joininfo nodes are only created and added to
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* 'current_joininfo_list' if a node for a particular join hasn't already
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* been created.
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*
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* 'current_joininfo_list' contains a list of those joininfo nodes that
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* have already been built
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* 'joininfo_list' is the list of join clauses involving this relation
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* 'join_relids' is a list of relids corresponding to the relations
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* currently being joined
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*
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* Returns a list of joininfo nodes, new and old.
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*/
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static List *
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new_joininfo_list(List *joininfo_list, Relids join_relids)
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{
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List *current_joininfo_list = NIL;
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Relids new_unjoined_relids = NIL;
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JoinInfo *other_joininfo = (JoinInfo *) NULL;
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List *xjoininfo = NIL;
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foreach(xjoininfo, joininfo_list)
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{
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List *or;
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JoinInfo *joininfo = (JoinInfo *) lfirst(xjoininfo);
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new_unjoined_relids = joininfo->unjoined_relids;
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foreach(or, new_unjoined_relids)
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{
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if (intMember(lfirsti(or), join_relids))
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new_unjoined_relids = lremove((void *) lfirst(or), new_unjoined_relids);
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}
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joininfo->unjoined_relids = new_unjoined_relids;
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if (new_unjoined_relids != NIL)
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{
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other_joininfo = joininfo_member(new_unjoined_relids,
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current_joininfo_list);
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if (other_joininfo)
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{
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other_joininfo->jinfo_restrictinfo = (List *)
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LispUnion(joininfo->jinfo_restrictinfo,
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other_joininfo->jinfo_restrictinfo);
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}
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else
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{
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other_joininfo = makeNode(JoinInfo);
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other_joininfo->unjoined_relids = joininfo->unjoined_relids;
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other_joininfo->jinfo_restrictinfo = joininfo->jinfo_restrictinfo;
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other_joininfo->mergejoinable = joininfo->mergejoinable;
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other_joininfo->hashjoinable = joininfo->hashjoinable;
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current_joininfo_list = lcons(other_joininfo,
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current_joininfo_list);
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}
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}
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}
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return current_joininfo_list;
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}
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/*
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* get_cheapest_complete_rel
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* Find the join relation that includes all the original
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* relations, i.e. the final join result.
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*
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* 'join_rel_list' is a list of join relations.
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*
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* Returns the list of final join relations.
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*/
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RelOptInfo *
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get_cheapest_complete_rel(List *join_rel_list)
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{
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List *xrel = NIL;
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RelOptInfo *final_rel = NULL;
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/*
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* find the relations that have no further joins, i.e., its joininfos
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* all have unjoined_relids nil.
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*/
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foreach(xrel, join_rel_list)
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{
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RelOptInfo *rel = (RelOptInfo *) lfirst(xrel);
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List *xjoininfo = NIL;
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bool final = true;
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foreach(xjoininfo, rel->joininfo)
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{
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JoinInfo *joininfo = (JoinInfo *) lfirst(xjoininfo);
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if (joininfo->unjoined_relids != NIL)
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{
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final = false;
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break;
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}
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}
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if (final)
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if (final_rel == NULL ||
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path_is_cheaper(rel->cheapestpath, final_rel->cheapestpath))
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final_rel = rel;
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}
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return final_rel;
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}
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static bool
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nonoverlap_sets(List *s1, List *s2)
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{
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List *x = NIL;
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foreach(x, s1)
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{
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int e = lfirsti(x);
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if (intMember(e, s2))
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return false;
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}
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return true;
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}
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static bool
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is_subset(List *s1, List *s2)
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{
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List *x = NIL;
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foreach(x, s1)
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{
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int e = lfirsti(x);
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if (!intMember(e, s2))
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return false;
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}
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return true;
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}
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static void
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set_joinrel_size(RelOptInfo *joinrel, RelOptInfo *outer_rel, RelOptInfo *inner_rel, JoinInfo *jinfo)
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{
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int ntuples;
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float selec;
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/*
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* voodoo magic. but better than a size of 0. I have no idea why we
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* didn't set the size before. -ay 2/95
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*/
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if (jinfo == NULL)
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{
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/* worst case: the cartesian product */
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ntuples = outer_rel->tuples * inner_rel->tuples;
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}
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else
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{
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selec = product_selec(jinfo->jinfo_restrictinfo);
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/* ntuples = Min(outer_rel->tuples,inner_rel->tuples) * selec; */
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ntuples = outer_rel->tuples * inner_rel->tuples * selec;
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}
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/*
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* I bet sizes less than 1 will screw up optimization so make the best
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* case 1 instead of 0 - jolly
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*/
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if (ntuples < 1)
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ntuples = 1;
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joinrel->tuples = ntuples;
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}
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