3 files changed, 35 insertions, 0 deletions
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index c82dde27263..4e833d79ef9 100644
--- a/doc/src/sgml/contrib.sgml
+++ b/doc/src/sgml/contrib.sgml
@@ -116,6 +116,7 @@ CREATE EXTENSION <replaceable>module_name</replaceable>;
  &isn;
  &lo;
  &ltree;
+ &oldsnapshot;
  &pageinspect;
  &passwordcheck;
  &pgbuffercache;
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index 828396d4a9e..47271addc14 100644
--- a/doc/src/sgml/filelist.sgml
+++ b/doc/src/sgml/filelist.sgml
@@ -129,6 +129,7 @@
 <!ENTITY lo              SYSTEM "lo.sgml">
 <!ENTITY ltree           SYSTEM "ltree.sgml">
 <!ENTITY oid2name        SYSTEM "oid2name.sgml">
+<!ENTITY oldsnapshot     SYSTEM "oldsnapshot.sgml">
 <!ENTITY pageinspect     SYSTEM "pageinspect.sgml">
 <!ENTITY passwordcheck   SYSTEM "passwordcheck.sgml">
 <!ENTITY pgbuffercache   SYSTEM "pgbuffercache.sgml">
diff --git a/doc/src/sgml/oldsnapshot.sgml b/doc/src/sgml/oldsnapshot.sgml
new file mode 100644
index 00000000000..a665ae72e78
--- /dev/null
+++ b/doc/src/sgml/oldsnapshot.sgml
@@ -0,0 +1,33 @@
+<!-- doc/src/sgml/oldsnapshot.sgml -->
+
+<sect1 id="oldsnapshot" xreflabel="old_snapshot">
+ <title>old_snapshot</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>
+  <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>