New cost model for planning, incorporating a penalty for random page

accesses versus sequential accesses, a (very crude) estimate of the
effects of caching on random page accesses, and cost to evaluate WHERE-
clause expressions.  Export critical parameters for this model as SET
variables.  Also, create SET variables for the planner's enable flags
(enable_seqscan, enable_indexscan, etc) so that these can be controlled
more conveniently than via PGOPTIONS.

Planner now estimates both startup cost (cost before retrieving
first tuple) and total cost of each path, so it can optimize queries
with LIMIT on a reasonable basis by interpolating between these costs.
Same facility is a win for EXISTS(...) subqueries and some other cases.

Redesign pathkey representation to achieve a major speedup in planning
(I saw as much as 5X on a 10-way join); also minor changes in planner
to reduce memory consumption by recycling discarded Path nodes and
not constructing unnecessary lists.

Minor cleanups to display more-plausible costs in some cases in
EXPLAIN output.

Initdb forced by change in interface to index cost estimation
functions.

1 files changed, 19 insertions, 12 deletions

diff --git a/src/include/optimizer/paths.h b/src/include/optimizer/paths.h
index 256aac90d75..d7a0cc2d546 100644
--- a/src/include/optimizer/paths.h
+++ b/src/include/optimizer/paths.h
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2000, PostgreSQL, Inc
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: paths.h,v 1.42 2000/02/07 04:41:04 tgl Exp $
+ * $Id: paths.h,v 1.43 2000/02/15 20:49:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -33,9 +33,9 @@ extern RelOptInfo *make_one_rel(Query *root);
  * indxpath.c
  *	  routines to generate index paths
  */
-extern List *create_index_paths(Query *root, RelOptInfo *rel, List *indices,
-								List *restrictinfo_list,
-								List *joininfo_list);
+extern void create_index_paths(Query *root, RelOptInfo *rel, List *indices,
+							   List *restrictinfo_list,
+							   List *joininfo_list);
 extern Oid indexable_operator(Expr *clause, Oid opclass, Oid relam,
 							  bool indexkey_on_left);
 extern List *extract_or_indexqual_conditions(RelOptInfo *rel,
@@ -47,14 +47,14 @@ extern List *expand_indexqual_conditions(List *indexquals);
  * orindxpath.c
  *	  additional routines for indexable OR clauses
  */
-extern List *create_or_index_paths(Query *root, RelOptInfo *rel,
-								   List *clauses);
+extern void create_or_index_paths(Query *root, RelOptInfo *rel,
+								  List *clauses);
 
 /*
  * tidpath.h
  *	  routines to generate tid paths
  */
-extern List *create_tidscan_paths(Query *root, RelOptInfo *rel);
+extern void create_tidscan_paths(Query *root, RelOptInfo *rel);
 
 /*
  * joinpath.c
@@ -89,20 +89,27 @@ typedef enum
 	PATHKEYS_DIFFERENT			/* neither pathkey includes the other */
 } PathKeysComparison;
 
+extern void add_equijoined_keys(Query *root, RestrictInfo *restrictinfo);
+extern List *canonicalize_pathkeys(Query *root, List *pathkeys);
 extern PathKeysComparison compare_pathkeys(List *keys1, List *keys2);
 extern bool pathkeys_contained_in(List *keys1, List *keys2);
 extern Path *get_cheapest_path_for_pathkeys(List *paths, List *pathkeys,
-											bool indexpaths_only);
+											CostSelector cost_criterion);
+extern Path *get_cheapest_fractional_path_for_pathkeys(List *paths,
+													   List *pathkeys,
+													   double fraction);
 extern List *build_index_pathkeys(Query *root, RelOptInfo *rel,
-								  IndexOptInfo *index);
+								  IndexOptInfo *index,
+								  ScanDirection scandir);
 extern List *build_join_pathkeys(List *outer_pathkeys,
-								 List *join_rel_tlist, List *joinclauses);
-extern bool commute_pathkeys(List *pathkeys);
+								 List *join_rel_tlist,
+								 List *equi_key_list);
 extern List *make_pathkeys_for_sortclauses(List *sortclauses,
 										   List *tlist);
 extern List *find_mergeclauses_for_pathkeys(List *pathkeys,
 											List *restrictinfos);
-extern List *make_pathkeys_for_mergeclauses(List *mergeclauses,
+extern List *make_pathkeys_for_mergeclauses(Query *root,
+											List *mergeclauses,
 											List *tlist);
 
 #endif	 /* PATHS_H */