<!-- $PostgreSQL: pgsql/doc/src/sgml/unaccent.sgml,v 1.6 2010/08/25 02:12:00 tgl Exp $ -->

<sect1 id="unaccent">

<title>unaccent</title>

</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

behavior. Currently, it supports most important accents from European

languages.

<filename>unaccent</> is a text search dictionary that removes accents

(diacritic signs) from lexemes.

It's a filtering dictionary, which means its output is

always passed to the next dictionary (if any), unlike the normal

behavior of dictionaries. This allows accent-insensitive processing

for full text search.

</para>

<para>

Limitation: Current implementation of <filename>unaccent</>

dictionary cannot be used as a normalizing dictionary for

<filename>thesaurus</filename> dictionary.

The current implementation of <filename>unaccent</> cannot be used as a

normalizing dictionary for the <filename>thesaurus</filename> dictionary.

</para>

<sect2>

<title>Configuration</title>

<para>

A <literal>unaccent</> dictionary accepts the following options:

An <literal>unaccent</> dictionary accepts the following options:

</para>

<itemizedlist>

<listitem>

<itemizedlist>

<listitem>

<para>

Each line represents pair: character_with_accent character_without_accent

Each line represents a pair, consisting of a character with accent

followed by a character without accent. The first is translated into

the second. For example,

<programlisting>

&Agrave; A

&Aacute; A

&Acirc;A

&Acirc; A

&Atilde; A

&Auml;A

&Aring;A

&AElig;A

&Auml; A

&Aring; A

&AElig; A

</programlisting>

</para>

</listitem>

</itemizedlist>

<para>

Look at <filename>unaccent.rules</>, which is installed in

<filename>$SHAREDIR/tsearch_data/</>, for an example.

A more complete example, which is directly useful for most European

languages, can be found in <filename>unaccent.rules</>, which is installed

in <filename>$SHAREDIR/tsearch_data/</> when the <filename>unaccent</>

module is installed.

</para>

</sect2>

<sect2>

<title>Usage</title>

<para>

Running the installation script creates a text search template

<literal>unaccent</> and a dictionary <literal>unaccent</>

Running the installation script<filename>unaccent.sql</>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');

mydb=# 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

To test the dictionary, you can try:

<programlisting>

=# select ts_lexize('unaccent','Hôtel');

ts_lexize

mydb=# select ts_lexize('unaccent','H&ocirc;tel');

ts_lexize

-----------

{Hotel}

(1 row)

</programlisting>

</para>

<para>

<programlisting>

=# CREATE TEXT SEARCH CONFIGURATION fr ( COPY = french );

=# ALTER TEXT SEARCH CONFIGURATION fr

mydb=# CREATE TEXT SEARCH CONFIGURATION fr ( COPY = french );

mydb=# 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

mydb=# select to_tsvector('fr','H&ocirc;tels de la Mer');

to_tsvector

-------------------

'hotel':1 'mer':4

(1 row)

=# select to_tsvector('fr','Hôtel de la Mer') @@ to_tsquery('fr','Hotels');

?column?

mydb=# select to_tsvector('fr','H&ocirc;tel 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

mydb=# select ts_headline('fr','H&ocirc;tel de la Mer',to_tsquery('fr','Hotels'));

ts_headline

------------------------

&lt;b&gt;Hôtel&lt;/b&gt;de la Mer

&lt;b&gt;H&ocirc;tel&lt;/b&gt;de la Mer

(1 row)

</programlisting>

</para>

</sect2>

<sect2>

<title>Function</title>

<title>Functions</title>

<para>

<function>unaccent</> function removes accents (diacritic signs) from

argument string. Basically, it's a wrapper around

<filename>unaccent</> dictionary.

The <function>unaccent()</> function removes accents (diacritic signs) from

a given string. Basically, it's a wrapper around the

<filename>unaccent</> dictionary, but it can be used outside normal

text search contexts.

</para>

<indexterm>

<primary>unaccent</primary>

</indexterm>

<synopsis>

unaccent(<optional><replaceable class="PARAMETER">dictionary</replaceable>, </optional> <replaceable class="PARAMETER">string</replaceable>)

returns <type>text</type>

unaccent(<optional><replaceable class="PARAMETER">dictionary</replaceable>, </optional> <replaceable class="PARAMETER">string</replaceable>) returns <type>text</type>

</synopsis>

<para>

For example:

<programlisting>

SELECT unaccent('unaccent', 'Hôtel');

SELECT unaccent('Hôtel');

SELECT unaccent('unaccent', 'H&ocirc;tel');

SELECT unaccent('H&ocirc;tel');

</programlisting>

</para>

</sect2>