|
|
|
@ -1,5 +1,5 @@ |
|
|
|
|
<!-- |
|
|
|
|
$Header: /cvsroot/pgsql/doc/src/sgml/perform.sgml,v 1.25 2003/01/27 22:40:56 momjian Exp $ |
|
|
|
|
$Header: /cvsroot/pgsql/doc/src/sgml/perform.sgml,v 1.26 2003/01/28 03:34:29 momjian Exp $ |
|
|
|
|
--> |
|
|
|
|
|
|
|
|
|
<chapter id="performance-tips"> |
|
|
|
@ -109,8 +109,8 @@ regression=# EXPLAIN SELECT * FROM tenk1; |
|
|
|
|
SELECT * FROM pg_class WHERE relname = 'tenk1'; |
|
|
|
|
</programlisting> |
|
|
|
|
|
|
|
|
|
you will find out that <classname>tenk1</classname> has 333 disk |
|
|
|
|
pages and 10000 rows. So the cost is estimated at 333 page |
|
|
|
|
you will find out that <classname>tenk1</classname> has 233 disk |
|
|
|
|
pages and 10000 rows. So the cost is estimated at 233 page |
|
|
|
|
reads, defined as costing 1.0 apiece, plus 10000 * <varname>cpu_tuple_cost</varname> which is |
|
|
|
|
currently 0.01 (try <command>SHOW cpu_tuple_cost</command>). |
|
|
|
|
</para> |
|
|
|
|