CREATE EXTENSION unaccent;
-- must have a UTF8 database
SELECT getdatabaseencoding();
 getdatabaseencoding 
---------------------
 UTF8
(1 row)

SET client_encoding TO 'UTF8';
SELECT unaccent('foobar');
 unaccent 
----------
 foobar
(1 row)

SELECT unaccent('ёлка');
 unaccent 
----------
 елка
(1 row)

SELECT unaccent('ЁЖИК');
 unaccent 
----------
 ЕЖИК
(1 row)

SELECT unaccent('˃˖˗˜');
 unaccent 
----------
 >+-~
(1 row)

SELECT unaccent('À');  -- Remove combining diacritical 0x0300
 unaccent 
----------
 A
(1 row)

SELECT unaccent('unaccent', 'foobar');
 unaccent 
----------
 foobar
(1 row)

SELECT unaccent('unaccent', 'ёлка');
 unaccent 
----------
 елка
(1 row)

SELECT unaccent('unaccent', 'ЁЖИК');
 unaccent 
----------
 ЕЖИК
(1 row)

SELECT unaccent('unaccent', '˃˖˗˜');
 unaccent 
----------
 >+-~
(1 row)

SELECT unaccent('unaccent', 'À');
 unaccent 
----------
 A
(1 row)

SELECT ts_lexize('unaccent', 'foobar');
 ts_lexize 
-----------
 
(1 row)

SELECT ts_lexize('unaccent', 'ёлка');
 ts_lexize 
-----------
 {елка}
(1 row)

SELECT ts_lexize('unaccent', 'ЁЖИК');
 ts_lexize 
-----------
 {ЕЖИК}
(1 row)

SELECT ts_lexize('unaccent', '˃˖˗˜');
 ts_lexize 
-----------
 {>+-~}
(1 row)

SELECT ts_lexize('unaccent', 'À');
 ts_lexize 
-----------
 {A}
(1 row)