up to 8 digits each, separated by a slash; for example,
    <literal>16/B374D848</literal>.  The <type>pg_lsn</type> type supports the
    standard comparison operators, like <literal>=</literal> and
    <literal>&gt;</literal>.  Two LSNs can be subtracted using the
    <literal>-</literal> operator; the result is the number of bytes separating
    those write-ahead log locations.  Also the number of bytes can be
    added into and subtracted from LSN using the
    <literal>+(pg_lsn,numeric)</literal> and
    <literal>-(pg_lsn,numeric)</literal> operators, respectively. Note that
    the calculated LSN should be in the range of <type>pg_lsn</type> type,
    i.e., between <literal>0/0</literal> and
    <literal>FFFFFFFF/FFFFFFFF</literal>.
   </para>
  </sect1>

  <sect1 id="datatype-pseudo">
   <title>Pseudo-Types</title>

   <indexterm zone="datatype-pseudo">
    <primary>record</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>any</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>anyelement</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>anyarray</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>anynonarray</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>anyenum</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>anyrange</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>anymultirange</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>anycompatible</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>anycompatiblearray</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>anycompatiblenonarray</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>anycompatiblerange</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>anycompatiblemultirange</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>void</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>trigger</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>event_trigger</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>pg_ddl_command</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>language_handler</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>fdw_handler</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>table_am_handler</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>index_am_handler</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>tsm_handler</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>cstring</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>internal</primary>
   </indexterm>

   <indexterm zone="datatype-pseudo">
    <primary>unknown</primary>
   </indexterm>

   <para>
    The <productname>PostgreSQL</productname> type system contains a
    number of special-purpose entries that are collectively called
    <firstterm>pseudo-types</firstterm>.  A pseudo-type cannot be used as a
    column data type, but it can be used to declare a function's
    argument or result type.  Each of the available pseudo-types is
    useful in situations where a function's behavior does not
    correspond to simply taking or returning a value of a specific
    <acronym>SQL</acronym> data type.  <xref
    linkend="datatype-pseudotypes-table"/> lists the existing
    pseudo-types.
   </para>

    <table id="datatype-pseudotypes-table">
     <title>Pseudo-Types</title>
     <tgroup cols="2">
      <colspec colname="col1" colwidth="2*"/>
      <colspec colname="col2" colwidth="3*"/>
      <thead>
       <row>
        <entry>Name</entry>
        <entry>Description</entry>