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Eliminate a lot of list-management overhead within join_search_one_level

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by adding a requirement that build_join_rel add new join RelOptInfos to the
appropriate list immediately at creation.  Per report from Robert Haas,
the list_concat_unique_ptr() calls that this change eliminates were taking
the lion's share of the runtime in larger join problems.  This doesn't do
anything to fix the fundamental combinatorial explosion in large join
problems, but it should push out the threshold of pain a bit further.

Note: because this changes the order in which joinrel lists are built,
it might result in changes in selected plans in cases where different
alternatives have exactly the same costs.  There is one example in the
regression tests.
This commit is contained in:
Tom Lane
2009-11-28 00:46:19 +00:00
parent fe83b975b2
commit 1a95f12702
9 changed files with 964 additions and 954 deletions
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5
src/include/optimizer/paths.h
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@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/optimizer/paths.h,v 1.108 2009/09/17 20:49:29 tgl Exp $
* $PostgreSQL: pgsql/src/include/optimizer/paths.h,v 1.109 2009/11/28 00:46:19 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -99,8 +99,7 @@ extern void add_paths_to_joinrel(PlannerInfo *root, RelOptInfo *joinrel,
* joinrels.c
* routines to determine which relations to join
*/
extern List *join_search_one_level(PlannerInfo *root, int level,
List **joinrels);
extern void join_search_one_level(PlannerInfo *root, int level);
extern RelOptInfo *make_join_rel(PlannerInfo *root,
RelOptInfo *rel1, RelOptInfo *rel2);
extern bool have_join_order_restriction(PlannerInfo *root,