150 lines
4.3 KiB
Plaintext
150 lines
4.3 KiB
Plaintext
<!-- doc/src/sgml/dict-xsyn.sgml -->
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<sect1 id="dict-xsyn" xreflabel="dict_xsyn">
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<title>dict_xsyn — example synonym full-text search dictionary</title>
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<indexterm zone="dict-xsyn">
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<primary>dict_xsyn</primary>
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</indexterm>
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<para>
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<filename>dict_xsyn</filename> (Extended Synonym Dictionary) is an example of an
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add-on dictionary template for full-text search. This dictionary type
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replaces words with groups of their synonyms, and so makes it possible to
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search for a word using any of its synonyms.
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</para>
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<sect2 id="dict-xsyn-config">
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<title>Configuration</title>
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<para>
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A <literal>dict_xsyn</literal> dictionary accepts the following 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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<literal>matchorig</literal> controls whether the original word is accepted by
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the dictionary. Default is <literal>true</literal>.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>matchsynonyms</literal> controls whether the synonyms are
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accepted by the dictionary. Default is <literal>false</literal>.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>keeporig</literal> controls whether the original word is included in
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the dictionary's output. Default is <literal>true</literal>.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>keepsynonyms</literal> controls whether the synonyms are included in
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the dictionary's output. Default is <literal>true</literal>.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>rules</literal> is the base name of the file containing the list of
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synonyms. This file must be stored in
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<filename>$SHAREDIR/tsearch_data/</filename> (where <literal>$SHAREDIR</literal> means
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the <productname>PostgreSQL</productname> installation's shared-data directory).
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Its name must end in <literal>.rules</literal> (which is not to be included in
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the <literal>rules</literal> parameter).
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</para>
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</listitem>
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</itemizedlist>
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<para>
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The rules file has the following format:
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</para>
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<itemizedlist>
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<listitem>
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<para>
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Each line represents a group of synonyms for a single word, which is
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given first on the line. Synonyms are separated by whitespace, thus:
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<programlisting>
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word syn1 syn2 syn3
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</programlisting>
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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 sharp (<literal>#</literal>) sign is a comment delimiter. It may appear at
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any position in a line. The rest of the line will be skipped.
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</para>
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</listitem>
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</itemizedlist>
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<para>
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Look at <filename>xsyn_sample.rules</filename>, which is installed in
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<filename>$SHAREDIR/tsearch_data/</filename>, for an example.
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</para>
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</sect2>
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<sect2 id="dict-xsyn-usage">
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<title>Usage</title>
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<para>
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Installing the <literal>dict_xsyn</literal> extension creates a text search
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template <literal>xsyn_template</literal> and a dictionary <literal>xsyn</literal>
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based on it, with 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 xsyn (RULES='my_rules', KEEPORIG=false);
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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('xsyn', 'word');
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ts_lexize
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-----------------------
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{syn1,syn2,syn3}
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mydb# ALTER TEXT SEARCH DICTIONARY xsyn (RULES='my_rules', KEEPORIG=true);
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ALTER TEXT SEARCH DICTIONARY
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mydb=# SELECT ts_lexize('xsyn', 'word');
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ts_lexize
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-----------------------
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{word,syn1,syn2,syn3}
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mydb# ALTER TEXT SEARCH DICTIONARY xsyn (RULES='my_rules', KEEPORIG=false, MATCHSYNONYMS=true);
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ALTER TEXT SEARCH DICTIONARY
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mydb=# SELECT ts_lexize('xsyn', 'syn1');
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ts_lexize
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-----------------------
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{syn1,syn2,syn3}
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mydb# ALTER TEXT SEARCH DICTIONARY xsyn (RULES='my_rules', KEEPORIG=true, MATCHORIG=false, KEEPSYNONYMS=false);
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ALTER TEXT SEARCH DICTIONARY
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mydb=# SELECT ts_lexize('xsyn', 'syn1');
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ts_lexize
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-----------------------
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{word}
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</programlisting>
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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 word, asciiword WITH xsyn, english_stem;
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</programlisting>
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</para>
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</sect2>
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</sect1>
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