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Postgres95 1.01 Distribution - Virgin Sources
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Marc G. Fournier
351
src/backend/optimizer/path/allpaths.c
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351
src/backend/optimizer/path/allpaths.c
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/*-------------------------------------------------------------------------
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*
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* allpaths.c--
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* Routines to find possible search paths for processing a query
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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/allpaths.c,v 1.1.1.1 1996/07/09 06:21:35 scrappy Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include <string.h>
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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 "nodes/primnodes.h"
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#include "optimizer/internal.h"
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#include "optimizer/paths.h"
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#include "optimizer/pathnode.h"
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#include "optimizer/clauses.h"
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#include "optimizer/xfunc.h"
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#include "optimizer/cost.h"
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#include "commands/creatinh.h"
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static void find_rel_paths(Query *root, List *rels);
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static List *find_join_paths(Query *root, List *outer_rels, int levels_left);
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/*
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* find-paths--
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* Finds all possible access paths for executing a query, returning the
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* top level list of relation entries.
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*
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* 'rels' is the list of single relation entries appearing in the query
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*/
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List *
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find_paths(Query *root, List *rels)
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{
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int levels_left;
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/*
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* Set the number of join (not nesting) levels yet to be processed.
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*/
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levels_left = length(rels);
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if (levels_left <= 0)
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return NIL;
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/*
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* Find the base relation paths.
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*/
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find_rel_paths(root, rels);
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if (levels_left <= 1) {
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/*
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* Unsorted single relation, no more processing is required.
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*/
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return (rels);
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}else {
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/*
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* this means that joins or sorts are required.
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* set selectivities of clauses that have not been set
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* by an index.
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*/
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set_rest_relselec(root, rels);
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return(find_join_paths(root, rels, levels_left-1));
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}
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}
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/*
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* find-rel-paths--
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* Finds all paths available for scanning each relation entry in
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* 'rels'. Sequential scan and any available indices are considered
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* if possible(indices are not considered for lower nesting levels).
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* All unique paths are attached to the relation's 'pathlist' field.
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*
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* MODIFIES: rels
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*/
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static void
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find_rel_paths(Query *root, List *rels)
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{
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List *temp;
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Rel *rel;
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List *lastpath;
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foreach(temp, rels) {
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List *sequential_scan_list;
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List *rel_index_scan_list;
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List *or_index_scan_list;
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rel = (Rel *)lfirst(temp);
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sequential_scan_list = lcons(create_seqscan_path(rel),
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NIL);
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rel_index_scan_list =
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find_index_paths(root,
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rel,
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find_relation_indices(root,rel),
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rel->clauseinfo,
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rel->joininfo);
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or_index_scan_list =
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create_or_index_paths(root, rel, rel->clauseinfo);
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rel->pathlist = add_pathlist(rel,
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sequential_scan_list,
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append(rel_index_scan_list,
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or_index_scan_list));
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/* The unordered path is always the last in the list.
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* If it is not the cheapest path, prune it.
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*/
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lastpath = rel->pathlist;
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while(lnext(lastpath)!=NIL)
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lastpath=lnext(lastpath);
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prune_rel_path(rel, (Path*)lfirst(lastpath));
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/*
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* if there is a qualification of sequential scan the selec.
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* value is not set -- so set it explicitly -- Sunita
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*/
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set_rest_selec(root, rel->clauseinfo);
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rel->size = compute_rel_size(rel);
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rel->width = compute_rel_width(rel);
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}
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return;
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}
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/*
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* find-join-paths--
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* Find all possible joinpaths for a query by successively finding ways
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* to join single relations into join relations.
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*
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* if BushyPlanFlag is set, bushy tree plans will be generated:
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* Find all possible joinpaths(bushy trees) for a query by systematically
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* finding ways to join relations(both original and derived) together.
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*
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* 'outer-rels' is the current list of relations for which join paths
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* are to be found, i.e., he current list of relations that
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* have already been derived.
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* 'levels-left' is the current join level being processed, where '1' is
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* the "last" level
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*
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* Returns the final level of join relations, i.e., the relation that is
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* the result of joining all the original relations togehter.
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*/
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static List *
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find_join_paths(Query *root, List *outer_rels, int levels_left)
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{
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List *x;
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List *new_rels;
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Rel *rel;
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/*
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* Determine all possible pairs of relations to be joined at this level.
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* Determine paths for joining these relation pairs and modify 'new-rels'
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* accordingly, then eliminate redundant join relations.
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*/
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new_rels = find_join_rels(root, outer_rels);
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find_all_join_paths(root, new_rels);
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new_rels = prune_joinrels(new_rels);
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#if 0
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/*
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** for each expensive predicate in each path in each distinct rel,
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** consider doing pullup -- JMH
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*/
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if (XfuncMode != XFUNC_NOPULL && XfuncMode != XFUNC_OFF)
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foreach(x, new_rels)
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xfunc_trypullup((Rel*)lfirst(x));
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#endif
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prune_rel_paths(new_rels);
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if(BushyPlanFlag) {
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/*
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* In case of bushy trees
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* if there is still a join between a join relation and another
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* relation, add a new joininfo that involves the join relation
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* to the joininfo list of the other relation
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*/
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add_new_joininfos(root, new_rels,outer_rels);
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}
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foreach(x, new_rels) {
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rel = (Rel*)lfirst(x);
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rel->size = compute_rel_size(rel);
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rel->width = compute_rel_width(rel);
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/*#define OPTIMIZER_DEBUG*/
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#ifdef OPTIMIZER_DEBUG
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printf("levels left: %d\n", levels_left);
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debug_print_rel(root, rel);
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#endif
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}
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if(BushyPlanFlag) {
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/*
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* prune rels that have been completely incorporated into
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* new join rels
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*/
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outer_rels = prune_oldrels(outer_rels);
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/*
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* merge join rels if then contain the same list of base rels
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*/
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outer_rels = merge_joinrels(new_rels,outer_rels);
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root->join_relation_list_ = outer_rels;
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}
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else {
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root->join_relation_list_ = new_rels;
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}
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if(levels_left == 1) {
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if(BushyPlanFlag)
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return(final_join_rels(outer_rels));
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else
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return(new_rels);
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} else {
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if(BushyPlanFlag)
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return(find_join_paths(root, outer_rels, levels_left - 1));
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else
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return(find_join_paths(root, new_rels, levels_left - 1));
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}
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}
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/*****************************************************************************
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*
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*****************************************************************************/
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static void
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print_joinclauses(Query *root, List *clauses)
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{
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List *l;
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extern void print_expr(Node *expr, List *rtable); /* in print.c */
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foreach(l, clauses) {
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CInfo *c = lfirst(l);
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print_expr((Node*)c->clause, root->rtable);
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if (lnext(l)) printf(" ");
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}
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}
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void
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print_path(Query *root, Path *path, int indent)
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{
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char *ptype = NULL;
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JoinPath *jp;
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bool join;
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int i;
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for(i=0; i < indent; i++)
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printf("\t");
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switch(nodeTag(path)) {
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case T_Path:
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ptype = "SeqScan"; join=false; break;
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case T_IndexPath:
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ptype = "IdxScan"; join=false; break;
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case T_JoinPath:
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ptype = "Nestloop"; join=true; break;
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case T_MergePath:
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ptype = "MergeJoin"; join=true; break;
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case T_HashPath:
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ptype = "HashJoin"; join=true; break;
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default:
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break;
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}
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if (join) {
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int size = path->parent->size;
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jp = (JoinPath*)path;
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printf("%s size=%d cost=%f\n", ptype, size, path->path_cost);
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switch(nodeTag(path)) {
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case T_MergePath:
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case T_HashPath:
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for(i=0; i < indent+1; i++)
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printf("\t");
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printf(" clauses=(");
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print_joinclauses(root,
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((JoinPath*)path)->pathclauseinfo);
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printf(")\n");
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if (nodeTag(path)==T_MergePath) {
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MergePath *mp = (MergePath*)path;
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if (mp->outersortkeys || mp->innersortkeys) {
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for(i=0; i < indent+1; i++)
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printf("\t");
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printf(" sortouter=%d sortinner=%d\n",
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((mp->outersortkeys)?1:0),
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((mp->innersortkeys)?1:0));
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}
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}
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break;
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default:
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break;
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}
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print_path(root, jp->outerjoinpath, indent+1);
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print_path(root, jp->innerjoinpath, indent+1);
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} else {
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int size = path->parent->size;
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int relid = lfirsti(path->parent->relids);
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printf("%s(%d) size=%d cost=%f",
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ptype, relid, size, path->path_cost);
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if (nodeTag(path)==T_IndexPath) {
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List *k, *l;
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printf(" keys=");
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foreach (k, path->keys) {
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printf("(");
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foreach (l, lfirst(k)) {
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Var *var = lfirst(l);
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printf("%d.%d", var->varnoold, var->varoattno);
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if (lnext(l)) printf(", ");
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}
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printf(")");
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if (lnext(k)) printf(", ");
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}
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}
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printf("\n");
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}
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}
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#ifdef OPTIMIZER_DEBUG
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static void
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debug_print_rel(Query *root, Rel *rel)
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{
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List *l;
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printf("(");
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foreach(l, rel->relids) {
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printf("%d ", lfirsti(l));
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}
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printf("): size=%d width=%d\n", rel->size, rel->width);
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printf("\tpath list:\n");
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foreach (l, rel->pathlist) {
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print_path(root, lfirst(l), 1);
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}
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printf("\tcheapest path:\n");
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print_path(root, rel->cheapestpath, 1);
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}
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#endif /* OPTIMIZER_DEBUG */
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