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Improve planning of Materialize nodes inserted atop the inner input of a

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mergejoin to shield it from doing mark/restore and refetches.  Put an explicit
flag in MergePath so we can centralize the logic that knows about this,
and add costing logic that considers using Materialize even when it's not
forced by the previously-existing considerations.  This is in response to
a discussion back in August that suggested that materializing an inner
indexscan can be helpful when the refetch percentage is high enough.
This commit is contained in:
Tom Lane
2009-11-15 02:45:35 +00:00
parent 29faadcd27
commit caf9c830d9
7 changed files with 125 additions and 116 deletions
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3
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 1.98 2009/09/12 22:12:04 tgl Exp $
* $PostgreSQL: pgsql/src/include/optimizer/cost.h,v 1.99 2009/11/15 02:45:35 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -84,7 +84,6 @@ extern void cost_recursive_union(Plan *runion, Plan *nrterm, Plan *rterm);
extern void cost_sort(Path *path, PlannerInfo *root,
List *pathkeys, Cost input_cost, double tuples, int width,
double limit_tuples);
extern bool sort_exceeds_work_mem(Sort *sort);
extern void cost_material(Path *path,
Cost input_startup_cost, Cost input_total_cost,
double tuples, int width);