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code cleanup; no major improvements yet. However, EXPLAIN does produce more intuitive outputs for nested loops with indexscans now...
345 lines
8.2 KiB
C
345 lines
8.2 KiB
C
/*-------------------------------------------------------------------------
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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 1.55 2000/01/09 00:26:29 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "optimizer/cost.h"
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#include "optimizer/geqo.h"
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#include "optimizer/internal.h"
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#include "optimizer/pathnode.h"
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#include "optimizer/paths.h"
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#ifdef GEQO
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bool _use_geqo_ = true;
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#else
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bool _use_geqo_ = false;
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#endif
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int32 _use_geqo_rels_ = GEQO_RELS;
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static void set_base_rel_pathlist(Query *root, List *rels);
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static RelOptInfo *make_one_rel_by_joins(Query *root, List *rels,
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int levels_needed);
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#ifdef OPTIMIZER_DEBUG
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static void debug_print_rel(Query *root, RelOptInfo *rel);
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#endif
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/*
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* make_one_rel
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* Finds all possible access paths for executing a query, returning a
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* single rel.
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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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RelOptInfo *
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make_one_rel(Query *root, List *rels)
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{
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int levels_needed;
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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_needed = length(rels);
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if (levels_needed <= 0)
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return NULL;
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/*
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* Generate access paths for the base rels.
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*/
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set_base_rel_pathlist(root, rels);
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if (levels_needed <= 1)
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{
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/*
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* Single relation, no more processing is required.
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*/
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return lfirst(rels);
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}
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else
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{
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/*
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* Generate join tree.
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*/
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return make_one_rel_by_joins(root, rels, levels_needed);
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}
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}
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/*
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* set_base_rel_pathlist
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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 useful 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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set_base_rel_pathlist(Query *root, List *rels)
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{
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List *temp;
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foreach(temp, rels)
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{
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RelOptInfo *rel = (RelOptInfo *) lfirst(temp);
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List *indices = find_relation_indices(root, rel);
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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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List *tidscan_pathlist;
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sequential_scan_list = lcons(create_seqscan_path(rel), NIL);
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/* Tid Scan Pathlist add */
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tidscan_pathlist = create_tidscan_paths(root, rel);
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if (tidscan_pathlist)
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sequential_scan_list = nconc(sequential_scan_list,
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tidscan_pathlist);
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rel_index_scan_list = create_index_paths(root,
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rel,
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indices,
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rel->restrictinfo,
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rel->joininfo);
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/* Note: create_or_index_paths depends on create_index_paths
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* to have marked OR restriction clauses with relevant indices;
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* this is why it doesn't need to be given the full list of indices.
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*/
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or_index_scan_list = create_or_index_paths(root, rel,
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rel->restrictinfo);
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/* add_pathlist will discard any paths that are dominated by
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* another available path, keeping only those paths that are
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* superior along at least one dimension of cost or sortedness.
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*/
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rel->pathlist = add_pathlist(rel,
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sequential_scan_list,
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nconc(rel_index_scan_list,
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or_index_scan_list));
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/* Now find the cheapest of the paths */
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set_cheapest(rel, rel->pathlist);
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/* Mark rel with estimated output rows and width */
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set_rel_rows_width(root, rel);
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}
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}
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/*
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* make_one_rel_by_joins
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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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* 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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* 'rels' is the current list of relations for which join paths
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* are to be found, i.e., the current list of relations that
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* have already been derived.
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* 'levels_needed' is the number of iterations needed
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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 together.
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*/
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static RelOptInfo *
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make_one_rel_by_joins(Query *root, List *rels, int levels_needed)
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{
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List *x;
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List *joined_rels = NIL;
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RelOptInfo *rel;
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/*******************************************
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* genetic query optimizer entry point *
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* <utesch@aut.tu-freiberg.de> *
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*******************************************/
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if ((_use_geqo_) && length(root->base_rel_list) >= _use_geqo_rels_)
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return geqo(root);
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/*******************************************
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* rest will be deprecated in case of GEQO *
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*******************************************/
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while (--levels_needed)
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{
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/*
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* Determine all possible pairs of relations to be joined at this
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* level. Determine paths for joining these relation pairs and
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* modify 'joined_rels' accordingly, then eliminate redundant join
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* relations.
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*/
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joined_rels = make_rels_by_joins(root, rels);
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update_rels_pathlist_for_joins(root, joined_rels);
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merge_rels_with_same_relids(joined_rels);
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root->join_rel_list = rels = joined_rels;
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#ifdef NOT_USED
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/*
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* * for each expensive predicate in each path in each distinct
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* rel, * 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, joined_rels)
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xfunc_trypullup((RelOptInfo *) lfirst(x));
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#endif
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rels_set_cheapest(root, joined_rels);
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foreach(x, joined_rels)
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{
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rel = (RelOptInfo *) lfirst(x);
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#ifdef OPTIMIZER_DEBUG
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printf("levels left: %d\n", levels_needed);
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debug_print_rel(root, rel);
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#endif
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}
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}
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return get_cheapest_complete_rel(rels);
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}
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/*****************************************************************************
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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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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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{
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RestrictInfo *c = lfirst(l);
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print_expr((Node *) c->clause, root->rtable);
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if (lnext(l))
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printf(" ");
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}
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}
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static 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 = false;
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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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{
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case T_Path:
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ptype = "SeqScan";
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join = false;
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break;
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case T_IndexPath:
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ptype = "IdxScan";
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join = false;
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break;
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case T_NestPath:
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ptype = "Nestloop";
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join = true;
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break;
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case T_MergePath:
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ptype = "MergeJoin";
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join = true;
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break;
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case T_HashPath:
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ptype = "HashJoin";
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join = true;
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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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{
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jp = (JoinPath *) path;
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printf("%s rows=%.0f cost=%f\n",
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ptype, path->parent->rows, path->path_cost);
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switch (nodeTag(path))
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{
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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, jp->path.parent->restrictinfo);
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printf(")\n");
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if (nodeTag(path) == T_MergePath)
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{
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MergePath *mp = (MergePath *) path;
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if (mp->outersortkeys || mp->innersortkeys)
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{
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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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}
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else
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{
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int relid = lfirsti(path->parent->relids);
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printf("%s(%d) rows=%.0f cost=%f\n",
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ptype, relid, path->parent->rows, path->path_cost);
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if (IsA(path, IndexPath))
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{
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printf(" pathkeys=");
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print_pathkeys(path->pathkeys, root->rtable);
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}
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}
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}
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static void
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debug_print_rel(Query *root, RelOptInfo *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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printf("): rows=%.0f width=%d\n", rel->rows, 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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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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