/*------------------------------------------------------------------------- * * pathnode.c-- * Routines to manipulate pathlists and create path nodes * * Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * $Header: /usr/local/cvsroot/pgsql/src/backend/optimizer/util/pathnode.c,v 1.6 1997/09/08 21:45:53 momjian Exp $ * *------------------------------------------------------------------------- */ #include #include "postgres.h" #include "nodes/relation.h" #include "utils/elog.h" #include "optimizer/internal.h" #include "optimizer/pathnode.h" #include "optimizer/clauseinfo.h" #include "optimizer/plancat.h" #include "optimizer/cost.h" #include "optimizer/keys.h" #include "optimizer/xfunc.h" #include "optimizer/ordering.h" #include "parser/parsetree.h" /* for getrelid() */ static Path *better_path(Path *new_path, List *unique_paths, bool *noOther); /***************************************************************************** * MISC. PATH UTILITIES *****************************************************************************/ /* * path-is-cheaper-- * Returns t iff 'path1' is cheaper than 'path2'. * */ bool path_is_cheaper(Path *path1, Path *path2) { Cost cost1 = path1->path_cost; Cost cost2 = path2->path_cost; return ((bool) (cost1 < cost2)); } /* * set_cheapest-- * Finds the minimum cost path from among a relation's paths. * * 'parent-rel' is the parent relation * 'pathlist' is a list of path nodes corresponding to 'parent-rel' * * Returns and sets the relation entry field with the pathnode that * is minimum. * */ Path * set_cheapest(Rel *parent_rel, List *pathlist) { List *p; Path *cheapest_so_far; Assert(pathlist != NIL); Assert(IsA(parent_rel, Rel)); cheapest_so_far = (Path *) lfirst(pathlist); foreach(p, lnext(pathlist)) { Path *path = (Path *) lfirst(p); if (path_is_cheaper(path, cheapest_so_far)) { cheapest_so_far = path; } } parent_rel->cheapestpath = cheapest_so_far; return (cheapest_so_far); } /* * add_pathlist-- * For each path in the list 'new-paths', add to the list 'unique-paths' * only those paths that are unique (i.e., unique ordering and ordering * keys). Should a conflict arise, the more expensive path is thrown out, * thereby pruning the plan space. But we don't prune if xfunc * told us not to. * * 'parent-rel' is the relation entry to which these paths correspond. * * Returns the list of unique pathnodes. * */ List * add_pathlist(Rel *parent_rel, List *unique_paths, List *new_paths) { List *x; Path *new_path; Path *old_path; bool noOther; foreach(x, new_paths) { new_path = (Path *) lfirst(x); if (member(new_path, unique_paths)) continue; old_path = better_path(new_path, unique_paths, &noOther); if (noOther) { /* Is a brand new path. */ new_path->parent = parent_rel; unique_paths = lcons(new_path, unique_paths); } else if (old_path == NULL) { ; /* do nothing if path is not cheaper */ } else if (old_path != NULL) { /* (IsA(old_path,Path)) { */ new_path->parent = parent_rel; if (!parent_rel->pruneable) { unique_paths = lcons(new_path, unique_paths); } else unique_paths = lcons(new_path, LispRemove(old_path, unique_paths)); } } return (unique_paths); } /* * better_path-- * Determines whether 'new-path' has the same ordering and keys as some * path in the list 'unique-paths'. If there is a redundant path, * eliminate the more expensive path. * * Returns: * The old path - if 'new-path' matches some path in 'unique-paths' and is * cheaper * nil - if 'new-path' matches but isn't cheaper * t - if there is no path in the list with the same ordering and keys * */ static Path * better_path(Path *new_path, List *unique_paths, bool *noOther) { Path *old_path = (Path *) NULL; Path *path = (Path *) NULL; List *temp = NIL; Path *retval = NULL; /* * XXX - added the following two lines which weren't int the lisp * planner, but otherwise, doesn't seem to work for the case where * new_path is 'nil */ foreach(temp, unique_paths) { path = (Path *) lfirst(temp); if ((equal_path_path_ordering(&new_path->p_ordering, &path->p_ordering) && samekeys(new_path->keys, path->keys))) { old_path = path; break; } } if (old_path == NULL) { *noOther = true; } else { *noOther = false; if (path_is_cheaper(new_path, old_path)) { retval = old_path; } } return (retval); } /***************************************************************************** * PATH NODE CREATION ROUTINES *****************************************************************************/ /* * create_seqscan_path-- * Creates a path corresponding to a sequential scan, returning the * pathnode. * */ Path * create_seqscan_path(Rel *rel) { int relid = 0; Path *pathnode = makeNode(Path); pathnode->pathtype = T_SeqScan; pathnode->parent = rel; pathnode->path_cost = 0.0; pathnode->p_ordering.ordtype = SORTOP_ORDER; pathnode->p_ordering.ord.sortop = NULL; pathnode->keys = NIL; /* * copy clauseinfo list into path for expensive function processing -- * JMH, 7/7/92 */ pathnode->locclauseinfo = (List *) copyObject((Node *) rel->clauseinfo); if (rel->relids != NULL) relid = lfirsti(rel->relids); pathnode->path_cost = cost_seqscan(relid, rel->pages, rel->tuples); /* add in expensive functions cost! -- JMH, 7/7/92 */ #if 0 if (XfuncMode != XFUNC_OFF) { pathnode->path_cost += xfunc_get_path_cost(pathnode); } #endif return (pathnode); } /* * create_index_path-- * Creates a single path node for an index scan. * * 'rel' is the parent rel * 'index' is the pathnode for the index on 'rel' * 'restriction-clauses' is a list of restriction clause nodes. * 'is-join-scan' is a flag indicating whether or not the index is being * considered because of its sort order. * * Returns the new path node. * */ IndexPath * create_index_path(Query *root, Rel *rel, Rel *index, List *restriction_clauses, bool is_join_scan) { IndexPath *pathnode = makeNode(IndexPath); pathnode->path.pathtype = T_IndexScan; pathnode->path.parent = rel; pathnode->path.p_ordering.ordtype = SORTOP_ORDER; pathnode->path.p_ordering.ord.sortop = index->ordering; pathnode->indexid = index->relids; pathnode->indexkeys = index->indexkeys; pathnode->indexqual = NIL; /* * copy clauseinfo list into path for expensive function processing -- * JMH, 7/7/92 */ pathnode->path.locclauseinfo = set_difference((List *) copyObject((Node *) rel->clauseinfo), (List *) restriction_clauses); /* * The index must have an ordering for the path to have (ordering) * keys, and vice versa. */ if (pathnode->path.p_ordering.ord.sortop) { pathnode->path.keys = collect_index_pathkeys(index->indexkeys, rel->targetlist); /* * Check that the keys haven't 'disappeared', since they may no * longer be in the target list (i.e., index keys that are not * relevant to the scan are not applied to the scan path node, so * if no index keys were found, we can't order the path). */ if (pathnode->path.keys == NULL) { pathnode->path.p_ordering.ord.sortop = NULL; } } else { pathnode->path.keys = NULL; } if (is_join_scan || restriction_clauses == NULL) { /* * Indices used for joins or sorting result nodes don't restrict * the result at all, they simply order it, so compute the scan * cost accordingly -- use a selectivity of 1.0. */ /* is the statement above really true? what about IndexScan as the inner of a join? */ pathnode->path.path_cost = cost_index(lfirsti(index->relids), index->pages, 1.0, rel->pages, rel->tuples, index->pages, index->tuples, false); /* add in expensive functions cost! -- JMH, 7/7/92 */ #if 0 if (XfuncMode != XFUNC_OFF) { pathnode->path_cost = (pathnode->path_cost + xfunc_get_path_cost((Path *) pathnode)); } #endif } else { /* * Compute scan cost for the case when 'index' is used with a * restriction clause. */ List *attnos; List *values; List *flags; float npages; float selec; Cost clausesel; get_relattvals(restriction_clauses, &attnos, &values, &flags); index_selectivity(lfirsti(index->relids), index->classlist, get_opnos(restriction_clauses), getrelid(lfirsti(rel->relids), root->rtable), attnos, values, flags, length(restriction_clauses), &npages, &selec); /* each clause gets an equal selectivity */ clausesel = pow(selec, 1.0 / (double) length(restriction_clauses)); pathnode->indexqual = restriction_clauses; pathnode->path.path_cost = cost_index(lfirsti(index->relids), (int) npages, selec, rel->pages, rel->tuples, index->pages, index->tuples, false); #if 0 /* add in expensive functions cost! -- JMH, 7/7/92 */ if (XfuncMode != XFUNC_OFF) { pathnode->path_cost += xfunc_get_path_cost((Path *) pathnode); } #endif /* * Set selectivities of clauses used with index to the selectivity * of this index, subdividing the selectivity equally over each of * the clauses. */ /* XXX Can this divide the selectivities in a better way? */ set_clause_selectivities(restriction_clauses, clausesel); } return (pathnode); } /* * create_nestloop_path-- * Creates a pathnode corresponding to a nestloop join between two * relations. * * 'joinrel' is the join relation. * 'outer_rel' is the outer join relation * 'outer_path' is the outer join path. * 'inner_path' is the inner join path. * 'keys' are the keys of the path * * Returns the resulting path node. * */ JoinPath * create_nestloop_path(Rel *joinrel, Rel *outer_rel, Path *outer_path, Path *inner_path, List *keys) { JoinPath *pathnode = makeNode(JoinPath); pathnode->path.pathtype = T_NestLoop; pathnode->path.parent = joinrel; pathnode->outerjoinpath = outer_path; pathnode->innerjoinpath = inner_path; pathnode->pathclauseinfo = joinrel->clauseinfo; pathnode->path.keys = keys; pathnode->path.joinid = NIL; pathnode->path.outerjoincost = (Cost) 0.0; pathnode->path.locclauseinfo = NIL; if (keys) { pathnode->path.p_ordering.ordtype = outer_path->p_ordering.ordtype; if (outer_path->p_ordering.ordtype == SORTOP_ORDER) { pathnode->path.p_ordering.ord.sortop = outer_path->p_ordering.ord.sortop; } else { pathnode->path.p_ordering.ord.merge = outer_path->p_ordering.ord.merge; } } else { pathnode->path.p_ordering.ordtype = SORTOP_ORDER; pathnode->path.p_ordering.ord.sortop = NULL; } pathnode->path.path_cost = cost_nestloop(outer_path->path_cost, inner_path->path_cost, outer_rel->size, inner_path->parent->size, page_size(outer_rel->size, outer_rel->width), IsA(inner_path, IndexPath)); /* add in expensive function costs -- JMH 7/7/92 */ #if 0 if (XfuncMode != XFUNC_OFF) { pathnode->path_cost += xfunc_get_path_cost((Path *) pathnode); } #endif return (pathnode); } /* * create_mergesort_path-- * Creates a pathnode corresponding to a mergesort join between * two relations * * 'joinrel' is the join relation * 'outersize' is the number of tuples in the outer relation * 'innersize' is the number of tuples in the inner relation * 'outerwidth' is the number of bytes per tuple in the outer relation * 'innerwidth' is the number of bytes per tuple in the inner relation * 'outer_path' is the outer path * 'inner_path' is the inner path * 'keys' are the new keys of the join relation * 'order' is the sort order required for the merge * 'mergeclauses' are the applicable join/restriction clauses * 'outersortkeys' are the sort varkeys for the outer relation * 'innersortkeys' are the sort varkeys for the inner relation * */ MergePath * create_mergesort_path(Rel *joinrel, int outersize, int innersize, int outerwidth, int innerwidth, Path *outer_path, Path *inner_path, List *keys, MergeOrder *order, List *mergeclauses, List *outersortkeys, List *innersortkeys) { MergePath *pathnode = makeNode(MergePath); pathnode->jpath.path.pathtype = T_MergeJoin; pathnode->jpath.path.parent = joinrel; pathnode->jpath.outerjoinpath = outer_path; pathnode->jpath.innerjoinpath = inner_path; pathnode->jpath.pathclauseinfo = joinrel->clauseinfo; pathnode->jpath.path.keys = keys; pathnode->jpath.path.p_ordering.ordtype = MERGE_ORDER; pathnode->jpath.path.p_ordering.ord.merge = order; pathnode->path_mergeclauses = mergeclauses; pathnode->jpath.path.locclauseinfo = NIL; pathnode->outersortkeys = outersortkeys; pathnode->innersortkeys = innersortkeys; pathnode->jpath.path.path_cost = cost_mergesort(outer_path->path_cost, inner_path->path_cost, outersortkeys, innersortkeys, outersize, innersize, outerwidth, innerwidth); /* add in expensive function costs -- JMH 7/7/92 */ #if 0 if (XfuncMode != XFUNC_OFF) { pathnode->path_cost += xfunc_get_path_cost((Path *) pathnode); } #endif return (pathnode); } /* * create_hashjoin_path-- XXX HASH * Creates a pathnode corresponding to a hash join between two relations. * * 'joinrel' is the join relation * 'outersize' is the number of tuples in the outer relation * 'innersize' is the number of tuples in the inner relation * 'outerwidth' is the number of bytes per tuple in the outer relation * 'innerwidth' is the number of bytes per tuple in the inner relation * 'outer_path' is the outer path * 'inner_path' is the inner path * 'keys' are the new keys of the join relation * 'operator' is the hashjoin operator * 'hashclauses' are the applicable join/restriction clauses * 'outerkeys' are the sort varkeys for the outer relation * 'innerkeys' are the sort varkeys for the inner relation * */ HashPath * create_hashjoin_path(Rel *joinrel, int outersize, int innersize, int outerwidth, int innerwidth, Path *outer_path, Path *inner_path, List *keys, Oid operator, List *hashclauses, List *outerkeys, List *innerkeys) { HashPath *pathnode = makeNode(HashPath); pathnode->jpath.path.pathtype = T_HashJoin; pathnode->jpath.path.parent = joinrel; pathnode->jpath.outerjoinpath = outer_path; pathnode->jpath.innerjoinpath = inner_path; pathnode->jpath.pathclauseinfo = joinrel->clauseinfo; pathnode->jpath.path.locclauseinfo = NIL; pathnode->jpath.path.keys = keys; pathnode->jpath.path.p_ordering.ordtype = SORTOP_ORDER; pathnode->jpath.path.p_ordering.ord.sortop = NULL; pathnode->jpath.path.outerjoincost = (Cost) 0.0; pathnode->jpath.path.joinid = (Relid) NULL; /* pathnode->hashjoinoperator = operator; */ pathnode->path_hashclauses = hashclauses; pathnode->outerhashkeys = outerkeys; pathnode->innerhashkeys = innerkeys; pathnode->jpath.path.path_cost = cost_hashjoin(outer_path->path_cost, inner_path->path_cost, outerkeys, innerkeys, outersize, innersize, outerwidth, innerwidth); /* add in expensive function costs -- JMH 7/7/92 */ #if 0 if (XfuncMode != XFUNC_OFF) { pathnode->path_cost += xfunc_get_path_cost((Path *) pathnode); } #endif return (pathnode); }