102 lines
3.1 KiB
Plaintext
102 lines
3.1 KiB
Plaintext
<!-- doc/src/sgml/dict-int.sgml -->
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<sect1 id="dict-int" xreflabel="dict_int">
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<title>dict_int —
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example full-text search dictionary for integers</title>
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<indexterm zone="dict-int">
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<primary>dict_int</primary>
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</indexterm>
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<para>
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<filename>dict_int</filename> is an example of an add-on dictionary template
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for full-text search. The motivation for this example dictionary is to
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control the indexing of integers (signed and unsigned), allowing such
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numbers to be indexed while preventing excessive growth in the number of
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unique words, which greatly affects the performance of searching.
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</para>
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<para>
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This module is considered <quote>trusted</quote>, that is, it can be
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installed by non-superusers who have <literal>CREATE</literal> privilege
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on the current database.
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</para>
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<sect2 id="dict-int-config">
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<title>Configuration</title>
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<para>
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The dictionary accepts three options:
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</para>
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<itemizedlist>
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<listitem>
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<para>
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The <literal>maxlen</literal> parameter specifies the maximum number of
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digits allowed in an integer word. The default value is 6.
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</para>
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</listitem>
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<listitem>
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<para>
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The <literal>rejectlong</literal> parameter specifies whether an overlength
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integer should be truncated or ignored. If <literal>rejectlong</literal> is
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<literal>false</literal> (the default), the dictionary returns the first
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<literal>maxlen</literal> digits of the integer. If <literal>rejectlong</literal> is
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<literal>true</literal>, the dictionary treats an overlength integer as a stop
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word, so that it will not be indexed. Note that this also means that
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such an integer cannot be searched for.
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</para>
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</listitem>
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<listitem>
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<para>
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The <literal>absval</literal> parameter specifies whether leading
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<quote><literal>+</literal></quote> or <quote><literal>-</literal></quote>
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signs should be removed from integer words. The default
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is <literal>false</literal>. When <literal>true</literal>, the sign is
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removed before <literal>maxlen</literal> is applied.
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</para>
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</listitem>
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</itemizedlist>
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</sect2>
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<sect2 id="dict-int-usage">
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<title>Usage</title>
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<para>
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Installing the <literal>dict_int</literal> extension creates a text search
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template <literal>intdict_template</literal> and a dictionary <literal>intdict</literal>
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based on it, with the default parameters. You can alter the
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parameters, for example
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<programlisting>
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mydb# ALTER TEXT SEARCH DICTIONARY intdict (MAXLEN = 4, REJECTLONG = true);
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ALTER TEXT SEARCH DICTIONARY
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</programlisting>
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or create new dictionaries based on the template.
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</para>
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<para>
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To test the dictionary, you can try
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<programlisting>
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mydb# select ts_lexize('intdict', '12345678');
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ts_lexize
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-----------
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{123456}
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</programlisting>
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but real-world usage will involve including it in a text search
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configuration as described in <xref linkend="textsearch"/>.
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That might look like this:
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<programlisting>
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ALTER TEXT SEARCH CONFIGURATION english
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ALTER MAPPING FOR int, uint WITH intdict;
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</programlisting>
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</para>
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</sect2>
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</sect1>
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