<literal>NOTICE</literal>, <literal>WARNING</literal>,
      and <literal>LOG</literal>. The default is <literal>LOG</literal>.
      Only superusers can change this setting.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="auto-explain-configuration-parameters-log-nested-statements">
    <term>
     <varname>auto_explain.log_nested_statements</varname> (<type>boolean</type>)
     <indexterm>
      <primary><varname>auto_explain.log_nested_statements</varname> configuration parameter</primary>
     </indexterm>
    </term>
    <listitem>
     <para>
      <varname>auto_explain.log_nested_statements</varname> causes nested
      statements (statements executed inside a function) to be considered
      for logging.  When it is off, only top-level query plans are logged. This
      parameter is off by default. Only superusers can change this setting.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="auto-explain-configuration-parameters-sample-rate">
    <term>
     <varname>auto_explain.sample_rate</varname> (<type>real</type>)
     <indexterm>
      <primary><varname>auto_explain.sample_rate</varname> configuration parameter</primary>
     </indexterm>
    </term>
    <listitem>
     <para>
      <varname>auto_explain.sample_rate</varname> causes auto_explain to only
      explain a fraction of the statements in each session.  The default is 1,
      meaning explain all the queries.  In case of nested statements, either all
      will be explained or none. Only superusers can change this setting.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>

  <para>
   In ordinary usage, these parameters are set
   in <filename>postgresql.conf</filename>, although superusers can alter them
   on-the-fly within their own sessions.
   Typical usage might be:
  </para>

<programlisting>
# postgresql.conf
session_preload_libraries = 'auto_explain'

auto_explain.log_min_duration = '3s'
</programlisting>
 </sect2>

 <sect2 id="auto-explain-example">
  <title>Example</title>

<programlisting>
postgres=# LOAD 'auto_explain';
postgres=# SET auto_explain.log_min_duration = 0;
postgres=# SET auto_explain.log_analyze = true;
postgres=# SELECT count(*)
           FROM pg_class, pg_index
           WHERE oid = indrelid AND indisunique;
</programlisting>

  <para>
   This might produce log output such as:
  </para>

<screen><![CDATA[
LOG:  duration: 3.651 ms  plan:
  Query Text: SELECT count(*)
              FROM pg_class, pg_index
              WHERE oid = indrelid AND indisunique;
  Aggregate  (cost=16.79..16.80 rows=1 width=0) (actual time=3.626..3.627 rows=1.00 loops=1)
    ->  Hash Join  (cost=4.17..16.55 rows=92 width=0) (actual time=3.349..3.594 rows=92.00 loops=1)
          Hash Cond: (pg_class.oid = pg_index.indrelid)
          ->  Seq Scan on pg_class  (cost=0.00..9.55 rows=255 width=4) (actual time=0.016..0.140 rows=255.00 loops=1)
          ->  Hash  (cost=3.02..3.02 rows=92 width=4) (actual time=3.238..3.238 rows=92.00 loops=1)
                Buckets: 1024  Batches: 1  Memory Usage: 4kB
                ->  Seq Scan on pg_index  (cost=0.00..3.02 rows=92 width=4) (actual time=0.008..3.187 rows=92.00 loops=1)
                      Filter: indisunique
]]></screen>
 </sect2>

 <sect2 id="auto-explain-author">
  <title>Author</title>

  <para>
   Takahiro Itagaki <email>itagaki.takahiro@oss.ntt.co.jp</email>
  </para>
 </sect2>

</sect1>