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In cost_mergejoin, the early-exit effect should not apply to the 

outer side of an outer join.  Per andrew@supernews.
This commit is contained in:
Tom Lane 2005-04-04 01:43:12 +00:00
parent 503edbdbff
commit 280de290d7
1 changed files with 12 additions and 7 deletions
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19
src/backend/optimizer/path/costsize.c
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@ -49,7 +49,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.140 2005/03/27 23:53:02 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.141 2005/04/04 01:43:12 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -917,16 +917,17 @@ cost_mergejoin(MergePath *path, Query *root)
rescanratio = 1.0 + (rescannedtuples / inner_path_rows);
/*
* A merge join will stop as soon as it exhausts either input stream.
* Estimate fraction of the left and right inputs that will actually
* need to be scanned. We use only the first (most significant) merge
* clause for this purpose.
* A merge join will stop as soon as it exhausts either input stream
* (unless it's an outer join, in which case the outer side has to be
* scanned all the way anyway). Estimate fraction of the left and right
* inputs that will actually need to be scanned. We use only the first
* (most significant) merge clause for this purpose.
*
* Since this calculation is somewhat expensive, and will be the same for
* all mergejoin paths associated with the merge clause, we cache the
* results in the RestrictInfo node.
*/
if (mergeclauses)
if (mergeclauses && path->jpath.jointype != JOIN_FULL)
{
firstclause = (RestrictInfo *) linitial(mergeclauses);
if (firstclause->left_mergescansel < 0) /* not computed yet? */
@ -946,10 +947,14 @@ cost_mergejoin(MergePath *path, Query *root)
outerscansel = firstclause->right_mergescansel;
innerscansel = firstclause->left_mergescansel;
}
if (path->jpath.jointype == JOIN_LEFT)
outerscansel = 1.0;
else if (path->jpath.jointype == JOIN_RIGHT)
innerscansel = 1.0;
}
else
{
/* cope with clauseless mergejoin */
/* cope with clauseless or full mergejoin */
outerscansel = innerscansel = 1.0;
}