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Teach tuplestore.c to throw away data before the "mark" point when the caller

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is using mark/restore but not rewind or backward-scan capability.  Insert a
materialize plan node between a mergejoin and its inner child if the inner
child is a sort that is expected to spill to disk.  The materialize shields
the sort from the need to do mark/restore and thereby allows it to perform
its final merge pass on-the-fly; while the materialize itself is normally
cheap since it won't spill to disk unless the number of tuples with equal
key values exceeds work_mem.

Greg Stark, with some kibitzing from Tom Lane.
This commit is contained in:
Tom Lane
2007-05-21 17:57:35 +00:00
parent 3963574d13
commit 2415ad9831
8 changed files with 236 additions and 40 deletions
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3
src/include/optimizer/cost.h
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@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/optimizer/cost.h,v 1.86 2007/05/04 01:13:45 tgl Exp $
* $PostgreSQL: pgsql/src/include/optimizer/cost.h,v 1.87 2007/05/21 17:57:34 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -75,6 +75,7 @@ extern void cost_valuesscan(Path *path, PlannerInfo *root,
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_cost, double tuples, int width);
extern void cost_agg(Path *path, PlannerInfo *root,