From 54f7f62d4ad5b06669ae4b37d9d05325a27f5755 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 1 Mar 2002 20:50:20 +0000
Subject: [PATCH] Fix thinko: cost_mergejoin must pay attention to which side
of the mergeclause is which when extracting selectivity info.
---
src/backend/optimizer/path/costsize.c | 43 ++++++++++++++++++---------
1 file changed, 29 insertions(+), 14 deletions(-)
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index a94d54342e4..e215a6cd366 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -42,7 +42,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.81 2002/03/01 06:01:19 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.82 2002/03/01 20:50:20 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -467,10 +467,11 @@ cost_sort(Path *path, Query *root,
}
/*
- * Note: should we bother to assign a nonzero run_cost to reflect the
- * overhead of extracting tuples from the sort result? Probably not
- * worth worrying about.
+ * Also charge a small amount (arbitrarily set equal to operator cost)
+ * per extracted tuple.
*/
+ run_cost += cpu_operator_cost * tuples;
+
path->startup_cost = startup_cost;
path->total_cost = startup_cost + run_cost;
}
@@ -567,11 +568,12 @@ cost_mergejoin(Path *path, Query *root,
Cost run_cost = 0;
Cost cpu_per_tuple;
RestrictInfo *firstclause;
+ Var *leftvar;
double outer_rows,
inner_rows;
double ntuples;
- Selectivity leftscan,
- rightscan;
+ Selectivity outerscansel,
+ innerscansel;
Path sort_path; /* dummy for result of cost_sort */
if (!enable_mergejoin)
@@ -592,11 +594,24 @@ cost_mergejoin(Path *path, Query *root,
mergejoinscansel(root, (Node *) firstclause->clause,
&firstclause->left_mergescansel,
&firstclause->right_mergescansel);
- leftscan = firstclause->left_mergescansel;
- rightscan = firstclause->right_mergescansel;
- outer_rows = outer_path->parent->rows * leftscan;
- inner_rows = inner_path->parent->rows * rightscan;
+ leftvar = get_leftop(firstclause->clause);
+ Assert(IsA(leftvar, Var));
+ if (intMember(leftvar->varno, outer_path->parent->relids))
+ {
+ /* left side of clause is outer */
+ outerscansel = firstclause->left_mergescansel;
+ innerscansel = firstclause->right_mergescansel;
+ }
+ else
+ {
+ /* left side of clause is inner */
+ outerscansel = firstclause->right_mergescansel;
+ innerscansel = firstclause->left_mergescansel;
+ }
+
+ outer_rows = outer_path->parent->rows * outerscansel;
+ inner_rows = inner_path->parent->rows * innerscansel;
/* cost of source data */
@@ -616,13 +631,13 @@ cost_mergejoin(Path *path, Query *root,
outer_path->parent->width);
startup_cost += sort_path.startup_cost;
run_cost += (sort_path.total_cost - sort_path.startup_cost)
- * leftscan;
+ * outerscansel;
}
else
{
startup_cost += outer_path->startup_cost;
run_cost += (outer_path->total_cost - outer_path->startup_cost)
- * leftscan;
+ * outerscansel;
}
if (innersortkeys) /* do we need to sort inner? */
@@ -635,13 +650,13 @@ cost_mergejoin(Path *path, Query *root,
inner_path->parent->width);
startup_cost += sort_path.startup_cost;
run_cost += (sort_path.total_cost - sort_path.startup_cost)
- * rightscan;
+ * innerscansel;
}
else
{
startup_cost += inner_path->startup_cost;
run_cost += (inner_path->total_cost - inner_path->startup_cost)
- * rightscan;
+ * innerscansel;
}
/*
--
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