-<!-- $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>