From 1379fb052fd18e87a5102e793bdb5b8bc2bf5d17 Mon Sep 17 00:00:00 2001
From: Bruce Momjian <bruce@momjian.us>
Date: Tue, 23 Feb 2010 02:47:27 +0000
Subject: [PATCH] Document that expression indexes that call functions allow
function-level statistics.
---
doc/src/sgml/maintenance.sgml | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
index ecec84cc2d9..0b01467ee01 100644
--- a/doc/src/sgml/maintenance.sgml
+++ b/doc/src/sgml/maintenance.sgml
@@ -1,4 +1,4 @@
-<!-- $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>
@@ -318,6 +318,14 @@
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>
--
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