From 77b7a740f95250af7d78f69e9c906c3e53f32e7b Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 13 Dec 2002 17:29:25 +0000
Subject: [PATCH] Adjust costsize calculations to avoid introducing unnecessary
roundoff error. This seems to explain the differing choice of plan that's
been causing geometry regress test to fail for the last few days.
---
src/backend/optimizer/path/costsize.c | 60 +++++++++++++++++++--------
1 file changed, 42 insertions(+), 18 deletions(-)
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 2125ff034f3..114e8798856 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 1.94 2002/12/12 15:49:28 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.95 2002/12/13 17:29:25 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -672,12 +672,22 @@ cost_nestloop(Path *path, Query *root,
*/
startup_cost += outer_path->startup_cost + inner_path->startup_cost;
run_cost += outer_path->total_cost - outer_path->startup_cost;
- run_cost += outer_path->parent->rows *
- (inner_path->total_cost - inner_path->startup_cost);
- if (!(IsA(inner_path, MaterialPath) ||
- IsA(inner_path, HashPath)) &&
- outer_path->parent->rows > 1)
- run_cost += (outer_path->parent->rows - 1) * inner_path->startup_cost;
+ if (IsA(inner_path, MaterialPath) ||
+ IsA(inner_path, HashPath))
+ {
+ /* charge only run cost for each iteration of inner path */
+ run_cost += outer_path->parent->rows *
+ (inner_path->total_cost - inner_path->startup_cost);
+ }
+ else
+ {
+ /*
+ * charge total cost for each iteration of inner path, except we
+ * already charged the first startup_cost in our own startup
+ */
+ run_cost += outer_path->parent->rows * inner_path->total_cost
+ - inner_path->startup_cost;
+ }
/*
* Number of tuples processed (not number emitted!). If inner path is
@@ -768,8 +778,8 @@ cost_mergejoin(Path *path, Query *root,
innerscansel = firstclause->left_mergescansel;
}
- outer_rows = outer_path->parent->rows * outerscansel;
- inner_rows = inner_path->parent->rows * innerscansel;
+ outer_rows = ceil(outer_path->parent->rows * outerscansel);
+ inner_rows = ceil(inner_path->parent->rows * innerscansel);
/* cost of source data */
@@ -1343,10 +1353,12 @@ approx_selectivity(Query *root, List *quals)
void
set_baserel_size_estimates(Query *root, RelOptInfo *rel)
{
+ double temp;
+
/* Should only be applied to base relations */
Assert(length(rel->relids) == 1);
- rel->rows = rel->tuples *
+ temp = rel->tuples *
restrictlist_selectivity(root,
rel->baserestrictinfo,
lfirsti(rel->relids));
@@ -1354,10 +1366,14 @@ set_baserel_size_estimates(Query *root, RelOptInfo *rel)
/*
* Force estimate to be at least one row, to make explain output look
* better and to avoid possible divide-by-zero when interpolating
- * cost.
+ * cost. Make it an integer, too.
*/
- if (rel->rows < 1.0)
- rel->rows = 1.0;
+ if (temp < 1.0)
+ temp = 1.0;
+ else
+ temp = ceil(temp);
+
+ rel->rows = temp;
rel->baserestrictcost = cost_qual_eval(rel->baserestrictinfo);
@@ -1437,10 +1453,12 @@ set_joinrel_size_estimates(Query *root, RelOptInfo *rel,
/*
* Force estimate to be at least one row, to make explain output look
* better and to avoid possible divide-by-zero when interpolating
- * cost.
+ * cost. Make it an integer, too.
*/
if (temp < 1.0)
temp = 1.0;
+ else
+ temp = ceil(temp);
rel->rows = temp;
@@ -1470,6 +1488,8 @@ set_joinrel_size_estimates(Query *root, RelOptInfo *rel,
void
set_function_size_estimates(Query *root, RelOptInfo *rel)
{
+ double temp;
+
/* Should only be applied to base relations that are functions */
Assert(length(rel->relids) == 1);
Assert(rel->rtekind == RTE_FUNCTION);
@@ -1483,7 +1503,7 @@ set_function_size_estimates(Query *root, RelOptInfo *rel)
rel->tuples = 1000;
/* Now estimate number of output rows */
- rel->rows = rel->tuples *
+ temp = rel->tuples *
restrictlist_selectivity(root,
rel->baserestrictinfo,
lfirsti(rel->relids));
@@ -1491,10 +1511,14 @@ set_function_size_estimates(Query *root, RelOptInfo *rel)
/*
* Force estimate to be at least one row, to make explain output look
* better and to avoid possible divide-by-zero when interpolating
- * cost.
+ * cost. Make it an integer, too.
*/
- if (rel->rows < 1.0)
- rel->rows = 1.0;
+ if (temp < 1.0)
+ temp = 1.0;
+ else
+ temp = ceil(temp);
+
+ rel->rows = temp;
rel->baserestrictcost = cost_qual_eval(rel->baserestrictinfo);
--
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