doc/src/sgml/dict-int.sgml

<!-- doc/src/sgml/dict-int.sgml -->

<sect1 id="dict-int" xreflabel="dict_int">
 <title>dict_int</title>

 <indexterm zone="dict-int">
  <primary>dict_int</primary>
 </indexterm>

 <para>
  <filename>dict_int</filename> is an example of an add-on dictionary template
  for full-text search.  The motivation for this example dictionary is to
  control the indexing of integers (signed and unsigned), allowing such
  numbers to be indexed while preventing excessive growth in the number of
  unique words, which greatly affects the performance of searching.
 </para>

 <para>
  This module is considered <quote>trusted</quote>, that is, it can be
  installed by non-superusers who have <literal>CREATE</literal> privilege
  on the current database.
 </para>

 <sect2>
  <title>Configuration</title>

  <para>
   The dictionary accepts three options:
  </para>

  <itemizedlist>
   <listitem>
    <para>
     The <literal>maxlen</literal> parameter specifies the maximum number of
     digits allowed in an integer word.  The default value is 6.
    </para>
   </listitem>
   <listitem>
    <para>
     The <literal>rejectlong</literal> parameter specifies whether an overlength
     integer should be truncated or ignored.  If <literal>rejectlong</literal> is
     <literal>false</literal> (the default), the dictionary returns the first
     <literal>maxlen</literal> digits of the integer. If <literal>rejectlong</literal> is
     <literal>true</literal>, the dictionary treats an overlength integer as a stop
     word, so that it will not be indexed.  Note that this also means that
     such an integer cannot be searched for.
    </para>
   </listitem>
   <listitem>
    <para>
     The <literal>absval</literal> parameter specifies whether leading
     <quote><literal>+</literal></quote> or <quote><literal>-</literal></quote>
     signs should be removed from integer words.  The default
     is <literal>false</literal>.  When <literal>true</literal>, the sign is
     removed before <literal>maxlen</literal> is applied.
    </para>
   </listitem>
  </itemizedlist>
 </sect2>

 <sect2>
  <title>Usage</title>

  <para>
   Installing the <literal>dict_int</literal> extension creates a text search
   template <literal>intdict_template</literal> and a dictionary <literal>intdict</literal>
   based on it, with the default parameters.  You can alter the
   parameters, for example

<programlisting>
mydb# ALTER TEXT SEARCH DICTIONARY intdict (MAXLEN = 4, REJECTLONG = true);
ALTER TEXT SEARCH DICTIONARY
</programlisting>

   or create new dictionaries based on the template.
  </para>

  <para>
   To test the dictionary, you can try

<programlisting>
mydb# select ts_lexize('intdict', '12345678');
 ts_lexize
-----------
 {123456}
</programlisting>

   but real-world usage will involve including it in a text search
   configuration as described in <xref linkend="textsearch"/>.
   That might look like this:

<programlisting>
ALTER TEXT SEARCH CONFIGURATION english
    ALTER MAPPING FOR int, uint WITH intdict;
</programlisting>

  </para>
 </sect2>

</sect1>