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Commite55985d

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committed
Tweak indexscan cost estimation: round estimated # of tuples visited up
to next integer. Previously, if selectivity was small, we could computevery tiny scan cost on the basis of estimating that only 0.001 tuplewould be fetched, which is silly. This naturally led to some rathersilly plans...
1 parent341dc91 commite55985d

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2 files changed

+10
-8
lines changed

2 files changed

+10
-8
lines changed

‎src/backend/optimizer/path/costsize.c

Lines changed: 5 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -42,7 +42,7 @@
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
45-
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.54 2000/03/22 22:08:33 tgl Exp $
45+
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.55 2000/03/30 00:53:29 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
@@ -262,11 +262,11 @@ cost_index(Path *path, Query *root,
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* effect. Would be nice to do better someday.
263263
*/
264264

265-
tuples_fetched=indexSelectivity*baserel->tuples;
265+
tuples_fetched=ceil(indexSelectivity*baserel->tuples);
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267267
if (tuples_fetched>0&&baserel->pages>0)
268-
pages_fetched=baserel->pages*
269-
log(tuples_fetched /baserel->pages+1.0);
268+
pages_fetched=ceil(baserel->pages*
269+
log(tuples_fetched /baserel->pages+1.0));
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else
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pages_fetched=tuples_fetched;
272272

@@ -594,7 +594,7 @@ cost_hashjoin(Path *path,
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* conservatively as the inner disbursion times the inner tuple count.
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*/
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run_cost+=cpu_operator_cost*outer_path->parent->rows*
597-
(inner_path->parent->rows*innerdisbursion);
597+
ceil(inner_path->parent->rows*innerdisbursion);
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599599
/*
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* Estimate the number of tuples that get through the hashing filter

‎src/backend/utils/adt/selfuncs.c

Lines changed: 5 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -15,13 +15,15 @@
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*
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*
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* IDENTIFICATION
18-
* $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.61 2000/03/23 00:55:42 tgl Exp $
18+
* $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.62 2000/03/30 00:53:30 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include"postgres.h"
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25+
#include<math.h>
26+
2527
#include"access/heapam.h"
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#include"catalog/catname.h"
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#include"catalog/pg_operator.h"
@@ -900,10 +902,10 @@ genericcostestimate(Query *root, RelOptInfo *rel,
900902
lfirsti(rel->relids));
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902904
/* Estimate the number of index tuples that will be visited */
903-
numIndexTuples=*indexSelectivity*index->tuples;
905+
numIndexTuples=ceil(*indexSelectivity*index->tuples);
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905907
/* Estimate the number of index pages that will be retrieved */
906-
numIndexPages=*indexSelectivity*index->pages;
908+
numIndexPages=ceil(*indexSelectivity*index->pages);
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908910
/*
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* Compute the index access cost.

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