Signed integer
 numhword        | Hyphenated word, letters and digits
 numword         | Word, letters and digits
 protocol        | Protocol head
 sfloat          | Scientific notation
 tag             | XML tag
 uint            | Unsigned integer
 url             | URL
 url_path        | URL path
 version         | Version number
 word            | Word, all letters
(23 rows)
</screen>
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
   <term><literal>\dFt<optional>+</optional> <optional>PATTERN</optional></literal></term>
    <listitem>
     <para>
      List text search templates (add <literal>+</literal> for more detail).
<screen>
=&gt; \dFt
                           List of text search templates
   Schema   |   Name    |                        Description
------------+-----------+-----------------------------------------------------------
 pg_catalog | ispell    | ispell dictionary
 pg_catalog | simple    | simple dictionary: just lower case and check for stopword
 pg_catalog | snowball  | snowball stemmer
 pg_catalog | synonym   | synonym dictionary: replace word by its synonym
 pg_catalog | thesaurus | thesaurus dictionary: phrase by phrase substitution
</screen>
     </para>
    </listitem>
   </varlistentry>
  </variablelist>

 </sect1>

 <sect1 id="textsearch-limitations">
  <title>Limitations</title>

  <para>
   The current limitations of <productname>PostgreSQL</productname>'s
   text search features are:
   <itemizedlist  spacing="compact" mark="bullet">
    <listitem>
     <para>The length of each lexeme must be less than 2 kilobytes</para>
    </listitem>
    <listitem>
     <para>The length of a <type>tsvector</type> (lexemes + positions) must be
     less than 1 megabyte</para>
    </listitem>
    <listitem>
     <!-- TODO: number of lexemes in what?  This is unclear -->
     <para>The number of lexemes must be less than
     2<superscript>64</superscript></para>
    </listitem>
    <listitem>
     <para>Position values in <type>tsvector</type> must be greater than 0 and
     no more than 16,383</para>
    </listitem>
    <listitem>
     <para>The match distance in a <literal>&lt;<replaceable>N</replaceable>&gt;</literal>
     (FOLLOWED BY) <type>tsquery</type> operator cannot be more than
     16,384</para>
    </listitem>
    <listitem>
     <para>No more than 256 positions per lexeme</para>
    </listitem>
    <listitem>
     <para>The number of nodes (lexemes + operators) in a <type>tsquery</type>
     must be less than 32,768</para>
    </listitem>
   </itemizedlist>
  </para>

  <para>
   For comparison, the <productname>PostgreSQL</productname> 8.1 documentation
   contained 10,441 unique words, a total of 335,420 words, and the most
   frequent word <quote>postgresql</quote> was mentioned 6,127 times in 655
   documents.
  </para>

   <!-- TODO we need to put a date on these numbers? -->
  <para>
   Another example &mdash; the <productname>PostgreSQL</productname> mailing
   list archives contained 910,989 unique words with 57,491,343 lexemes in
   461,020 messages.
  </para>

 </sect1>

</chapter>