public function loadCount()
    {
        $query = $this->source()->sqlLoadCount();

        $db = $this->source()->db();
        if (!$db) {
            throw new RuntimeException(
                'Could not instanciate a database connection.'
            );
        }
        $this->logger->debug($query);

        $sth = $db->prepare($query);
        $sth->execute();
        $res = $sth->fetchColumn(0);

        return (int)$res;
    }