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Add an 'enable_material' GUC.

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The logic for determining whether to materialize has been significantly
overhauled for 9.0.  In case there should be any doubt about whether
materialization is a win in any particular case, this should provide a
convenient way of seeing what happens without it; but even with enable_material
turned off, we still materialize in cases where it is required for
correctness.

Thanks to Tom Lane for the review.
This commit is contained in:
Robert Haas
2010-04-19 00:55:26 +00:00
parent 9287567eff
commit 5b89ef384c
8 changed files with 57 additions and 15 deletions
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10
src/backend/optimizer/path/joinpath.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/joinpath.c,v 1.132 2010/03/28 22:59:32 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/joinpath.c,v 1.133 2010/04/19 00:55:25 rhaas Exp $
*
*-------------------------------------------------------------------------
*/
@ -437,10 +437,12 @@ match_unsorted_outer(PlannerInfo *root,
else if (nestjoinOK)
{
/*
* Consider materializing the cheapest inner path, unless it is one
* that materializes its output anyway.
* Consider materializing the cheapest inner path, unless
* enable_material is off or the path in question materializes its
* output anyway.
*/
if (!ExecMaterializesOutput(inner_cheapest_total->pathtype))
if (enable_material &&
!ExecMaterializesOutput(inner_cheapest_total->pathtype))
matpath = (Path *)
create_material_path(innerrel, inner_cheapest_total);