<!-- doc/src/sgml/oldsnapshot.sgml -->

<sect1 id="oldsnapshot" xreflabel="old_snapshot">
 <title>old_snapshot &mdash; inspect <literal>old_snapshot_threshold</literal> state</title>

 <indexterm zone="oldsnapshot">
  <primary>old_snapshot</primary>
 </indexterm>

 <para>
  The <filename>old_snapshot</filename> module allows inspection
  of the server state that is used to implement
  <xref linkend="guc-old-snapshot-threshold" />.
 </para>

 <sect2 id="oldsnapshot-functions">
  <title>Functions</title>

  <variablelist>
   <varlistentry>
    <term><function>pg_old_snapshot_time_mapping(array_offset OUT int4, end_timestamp OUT timestamptz, newest_xmin OUT xid) returns setof record</function></term>
    <listitem>
     <para>
      Returns all of the entries in the server's timestamp to XID mapping.
      Each entry represents the newest xmin of any snapshot taken in the
      corresponding minute.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>
 </sect2>

</sect1>
