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-rw-r--r--doc/src/sgml/ref/create_index.sgml10
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diff --git a/doc/src/sgml/ref/create_index.sgml b/doc/src/sgml/ref/create_index.sgml
index 749db2845e8..844f00904be 100644
--- a/doc/src/sgml/ref/create_index.sgml
+++ b/doc/src/sgml/ref/create_index.sgml
@@ -746,6 +746,16 @@ Indexes:
</para>
<para>
+ The regularly system collects statistics on all of a table's
+ columns. Newly-created non-expression indexes can immediately
+ use these statistics to determine an index's usefulness.
+ For new expression indexes, it is necessary to run <link
+ linkend="sql-analyze"><command>ANALYZE</command></link> or wait for
+ the <link linkend="autovacuum">autovacuum daemon</link> to analyze
+ the table to generate statistics about new expression indexes.
+ </para>
+
+ <para>
For most index methods, the speed of creating an index is
dependent on the setting of <xref linkend="guc-maintenance-work-mem"/>.
Larger values will reduce the time needed for index creation, so long