<!-- $PostgreSQL: pgsql/doc/src/sgml/maintenance.sgml,v 1.99 2010/02/08 04:33:51 tgl Exp $ -->

<!-- $PostgreSQL: pgsql/doc/src/sgml/maintenance.sgml,v 1.100 2010/02/23 02:47:27 momjian Exp $ -->

<chapter id="maintenance">

<title>Routine Database Maintenance Tasks</title>

SET STATISTICS</>, or change the database-wide default using the <xref

linkend="guc-default-statistics-target"> configuration parameter.

</para>

<para>

Also, by default there is limited information available about

the selectivity of functions. However, if you create an expression

index that uses a function call, useful statistics will be

gathered about the function, which can greatly improve query

plans that use the expression index.

</para>

</tip>

</sect2>