database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-06-16 06:01:02 +03:00
Code Activity

Tweak indexscan cost estimation: round estimated # of tuples visited up

Browse Source 
to next integer.  Previously, if selectivity was small, we could compute
very tiny scan cost on the basis of estimating that only 0.001 tuple
would be fetched, which is silly.  This naturally led to some rather
silly plans...
This commit is contained in:
Tom Lane
2000-03-30 00:53:30 +00:00
parent 341dc91820
commit e55985d3be
2 changed files with 10 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
src/backend/utils/adt/selfuncs.c
View File

@ -15,13 +15,15 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.61 2000/03/23 00:55:42 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.62 2000/03/30 00:53:30 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <math.h>
#include "access/heapam.h"
#include "catalog/catname.h"
#include "catalog/pg_operator.h"
@ -900,10 +902,10 @@ genericcostestimate(Query *root, RelOptInfo *rel,
lfirsti(rel->relids));
/* Estimate the number of index tuples that will be visited */
numIndexTuples = *indexSelectivity * index->tuples;
numIndexTuples = ceil(*indexSelectivity * index->tuples);
/* Estimate the number of index pages that will be retrieved */
numIndexPages = *indexSelectivity * index->pages;
numIndexPages = ceil(*indexSelectivity * index->pages);
/*
* Compute the index access cost.