diff options
Diffstat (limited to 'doc/src/sgml/unaccent.sgml')
| -rw-r--r-- | doc/src/sgml/unaccent.sgml | 150 |
1 files changed, 150 insertions, 0 deletions
diff --git a/doc/src/sgml/unaccent.sgml b/doc/src/sgml/unaccent.sgml new file mode 100644 index 0000000000..b3c7bbee48 --- /dev/null +++ b/doc/src/sgml/unaccent.sgml @@ -0,0 +1,150 @@ +<sect1 id="unaccent"> + <title>unaccent</title> + + <indexterm zone="unaccent"> + <primary>unaccent</primary> + </indexterm> + + <para> + <filename>unaccent</> removes accents (diacritic signs) from a lexeme. + It's a filtering dictionary, that means its output is + always passed to the next dictionary (if any), contrary to the standard + behaviour. Currently, it supports most important accents from european + languages. + </para> + + <para> + Limitation: Current implementation of <filename>unaccent</> + dictionary cannot be used as a normalizing dictionary for + <filename>thesaurus</filename> dictionary. + </para> + + <sect2> + <title>Configuration</title> + + <para> + A <literal>unaccent</> dictionary accepts the following options: + </para> + <itemizedlist> + <listitem> + <para> + <literal>RULES</> is the base name of the file containing the list of + translation rules. This file must be stored in + <filename>$SHAREDIR/tsearch_data/</> (where <literal>$SHAREDIR</> means + the <productname>PostgreSQL</> installation's shared-data directory). + Its name must end in <literal>.rules</> (which is not to be included in + the <literal>RULES</> parameter). + </para> + </listitem> + </itemizedlist> + <para> + The rules file has the following format: + </para> + <itemizedlist> + <listitem> + <para> + Each line represents pair: character_with_accent character_without_accent + <programlisting> +À A +Á A +Â A +Ã A +Ä A +Å A +Æ A + </programlisting> + </para> + </listitem> + </itemizedlist> + + <para> + Look at <filename>unaccent.rules</>, which is installed in + <filename>$SHAREDIR/tsearch_data/</>, for an example. + </para> + </sect2> + + <sect2> + <title>Usage</title> + + <para> + Running the installation script creates a text search template + <literal>unaccent</> and a dictionary <literal>unaccent</> + based on it, with default parameters. You can alter the + parameters, for example + +<programlisting> +=# ALTER TEXT SEARCH DICTIONARY unaccent (RULES='my_rules'); +</programlisting> + + or create new dictionaries based on the template. + </para> + + <para> + To test the dictionary, you can try + +<programlisting> +=# select ts_lexize('unaccent','Hôtel'); + ts_lexize +----------- + {Hotel} +(1 row) +</programlisting> + </para> + + <para> + Filtering dictionary are useful for correct work of + <function>ts_headline</function> function. +<programlisting> +=# CREATE TEXT SEARCH CONFIGURATION fr ( COPY = french ); +=# ALTER TEXT SEARCH CONFIGURATION fr + ALTER MAPPING FOR hword, hword_part, word + WITH unaccent, french_stem; +=# select to_tsvector('fr','Hôtels de la Mer'); + to_tsvector +------------------- + 'hotel':1 'mer':4 +(1 row) + +=# select to_tsvector('fr','Hôtel de la Mer') @@ to_tsquery('fr','Hotels'); + ?column? +---------- + t +(1 row) +=# select ts_headline('fr','Hôtel de la Mer',to_tsquery('fr','Hotels')); + ts_headline +------------------------ + <b>Hôtel</b>de la Mer +(1 row) + +</programlisting> + </para> + </sect2> + + <sect2> + <title>Function</title> + + <para> + <function>unaccent</> function removes accents (diacritic signs) from + argument string. Basically, it's a wrapper around + <filename>unaccent</> dictionary. + </para> + + <indexterm> + <primary>unaccent</primary> + </indexterm> + + <synopsis> + unaccent(<optional><replaceable class="PARAMETER">dictionary</replaceable>, + </optional> <replaceable class="PARAMETER">string</replaceable>) + returns <type>text</type> + </synopsis> + + <para> +<programlisting> +SELECT unaccent('unaccent','Hôtel'); +SELECT unaccent('Hôtel'); +</programlisting> + </para> + </sect2> + +</sect1> |