Help:Patching MediaWiki for PostgreSQL UTF-8 access
To allow proper character set translation/verification within the PostgreSQL backend, the server needs to know what the client encoding is set to. Some PostgreSQL installations use other than UTF8 default client encoding, even when the database cluster has been initialized with UTF-8 (the default with most modern installations).
In this case, MediaWiki fails to set the proper encoding after the open call to the database. To fix this, apply the following patch against mediawiki/includes/db/DatabasePostgres.php (just before the "return" statement in the "open" function):
187a188 > $this->doQuery('SET client_encoding="UTF8"');