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>Appendix F. Additional Supplied Modules</TD
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><H1
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><A
NAME="DICT-XSYN"
>F.11. dict_xsyn</A
></H1
><P
> <TT
CLASS="FILENAME"
>dict_xsyn</TT
> (Extended Synonym Dictionary) is an example of an
add-on dictionary template for full-text search. This dictionary type
replaces words with groups of their synonyms, and so makes it possible to
search for a word using any of its synonyms.
</P
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN147983"
>F.11.1. Configuration</A
></H2
><P
> A <TT
CLASS="LITERAL"
>dict_xsyn</TT
> dictionary accepts the following options:
</P
><P
></P
><UL
><LI
><P
> <TT
CLASS="LITERAL"
>matchorig</TT
> controls whether the original word is accepted by
the dictionary. Default is <TT
CLASS="LITERAL"
>true</TT
>.
</P
></LI
><LI
><P
> <TT
CLASS="LITERAL"
>matchsynonyms</TT
> controls whether the synonyms are
accepted by the dictionary. Default is <TT
CLASS="LITERAL"
>false</TT
>.
</P
></LI
><LI
><P
> <TT
CLASS="LITERAL"
>keeporig</TT
> controls whether the original word is included in
the dictionary's output. Default is <TT
CLASS="LITERAL"
>true</TT
>.
</P
></LI
><LI
><P
> <TT
CLASS="LITERAL"
>keepsynonyms</TT
> controls whether the synonyms are included in
the dictionary's output. Default is <TT
CLASS="LITERAL"
>true</TT
>.
</P
></LI
><LI
><P
> <TT
CLASS="LITERAL"
>rules</TT
> is the base name of the file containing the list of
synonyms. This file must be stored in
<TT
CLASS="FILENAME"
>$SHAREDIR/tsearch_data/</TT
> (where <TT
CLASS="LITERAL"
>$SHAREDIR</TT
> means
the <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> installation's shared-data directory).
Its name must end in <TT
CLASS="LITERAL"
>.rules</TT
> (which is not to be included in
the <TT
CLASS="LITERAL"
>rules</TT
> parameter).
</P
></LI
></UL
><P
> The rules file has the following format:
</P
><P
></P
><UL
><LI
><P
> Each line represents a group of synonyms for a single word, which is
given first on the line. Synonyms are separated by whitespace, thus:
</P><PRE
CLASS="PROGRAMLISTING"
>word syn1 syn2 syn3</PRE
><P>
</P
></LI
><LI
><P
> The sharp (<TT
CLASS="LITERAL"
>#</TT
>) sign is a comment delimiter. It may appear at
any position in a line. The rest of the line will be skipped.
</P
></LI
></UL
><P
> Look at <TT
CLASS="FILENAME"
>xsyn_sample.rules</TT
>, which is installed in
<TT
CLASS="FILENAME"
>$SHAREDIR/tsearch_data/</TT
>, for an example.
</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN148023"
>F.11.2. Usage</A
></H2
><P
> Installing the <TT
CLASS="LITERAL"
>dict_xsyn</TT
> extension creates a text search
template <TT
CLASS="LITERAL"
>xsyn_template</TT
> and a dictionary <TT
CLASS="LITERAL"
>xsyn</TT
>
based on it, with default parameters. You can alter the
parameters, for example
</P><PRE
CLASS="PROGRAMLISTING"
>mydb# ALTER TEXT SEARCH DICTIONARY xsyn (RULES='my_rules', KEEPORIG=false);
ALTER TEXT SEARCH DICTIONARY</PRE
><P>
or create new dictionaries based on the template.
</P
><P
> To test the dictionary, you can try
</P><PRE
CLASS="PROGRAMLISTING"
>mydb=# SELECT ts_lexize('xsyn', 'word');
ts_lexize
-----------------------
{syn1,syn2,syn3}
mydb# ALTER TEXT SEARCH DICTIONARY xsyn (RULES='my_rules', KEEPORIG=true);
ALTER TEXT SEARCH DICTIONARY
mydb=# SELECT ts_lexize('xsyn', 'word');
ts_lexize
-----------------------
{word,syn1,syn2,syn3}
mydb# ALTER TEXT SEARCH DICTIONARY xsyn (RULES='my_rules', KEEPORIG=false, MATCHSYNONYMS=true);
ALTER TEXT SEARCH DICTIONARY
mydb=# SELECT ts_lexize('xsyn', 'syn1');
ts_lexize
-----------------------
{syn1,syn2,syn3}
mydb# ALTER TEXT SEARCH DICTIONARY xsyn (RULES='my_rules', KEEPORIG=true, MATCHORIG=false, KEEPSYNONYMS=false);
ALTER TEXT SEARCH DICTIONARY
mydb=# SELECT ts_lexize('xsyn', 'syn1');
ts_lexize
-----------------------
{word}</PRE
><P>
Real-world usage will involve including it in a text search
configuration as described in <A
HREF="textsearch.html"
>Chapter 12</A
>.
That might look like this:
</P><PRE
CLASS="PROGRAMLISTING"
>ALTER TEXT SEARCH CONFIGURATION english
ALTER MAPPING FOR word, asciiword WITH xsyn, english_stem;</PRE
><P>
</P
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