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If we expect a hash join to be performed in multiple batches, suppress

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"physical tlist" optimization on the outer relation (ie, force a projection
step to occur in its scan).  This avoids storing useless column values when
the outer relation's tuples are written to temporary batch files.

Modified version of a patch by Michael Henderson and Ramon Lawrence.
This commit is contained in:
Tom Lane
2009-03-26 17:15:35 +00:00
parent ee4c187f64
commit f38fbf31f5
5 changed files with 25 additions and 6 deletions
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4
src/backend/optimizer/path/costsize.c
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@ -54,7 +54,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.205 2009/03/21 00:04:39 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.206 2009/03/26 17:15:35 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -1880,6 +1880,8 @@ cost_hashjoin(HashPath *path, PlannerInfo *root, SpecialJoinInfo *sjinfo)
&numbatches,
&num_skew_mcvs);
virtualbuckets = (double) numbuckets *(double) numbatches;
/* mark the path with estimated # of batches */
path->num_batches = numbatches;
/*
* Determine bucketsize fraction for inner relation. We use the smallest