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Rewrite the planner's handling of materialized plan types so that there is

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an explicit model of rescan costs being different from first-time costs.
The costing of Material nodes in particular now has some visible relationship
to the actual runtime behavior, where before it was essentially fantasy.
This also fixes up a couple of places where different materialized plan types
were treated differently for no very good reason (probably just oversights).

A couple of the regression tests are affected, because the planner now chooses
to put the other relation on the inside of a nestloop-with-materialize.
So far as I can see both changes are sane, and the planner is now more
consistently following the expectation that it should prefer to materialize
the smaller of two relations.

Per a recent discussion with Robert Haas.
This commit is contained in:
Tom Lane
2009-09-12 22:12:09 +00:00
parent 5f1b32ddf8
commit 9bb342811b
12 changed files with 1029 additions and 916 deletions
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5
src/include/optimizer/cost.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/cost.h,v 1.97 2009/06/11 14:49:11 momjian Exp $
* $PostgreSQL: pgsql/src/include/optimizer/cost.h,v 1.98 2009/09/12 22:12:04 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -86,7 +86,8 @@ extern void cost_sort(Path *path, PlannerInfo *root,
double limit_tuples);
extern bool sort_exceeds_work_mem(Sort *sort);
extern void cost_material(Path *path,
Cost input_cost, double tuples, int width);
Cost input_startup_cost, Cost input_total_cost,
double tuples, int width);
extern void cost_agg(Path *path, PlannerInfo *root,
AggStrategy aggstrategy, int numAggs,
int numGroupCols, double numGroups,