private function getConnectionString() {
        $parameters = array(
            'host='             . $this->getHost(),
            'connect_timeout='  . $this->getConnectTimeout(),
            'user='             . $this->getUserName(),
        );
        $this->hasPort()        && $parameters[] = 'port='      . $this->getPort();
        $this->hasPassword()    && $parameters[] = 'password='  . $this->getPassword();
        $this->hasDatabase()    && $parameters[] = 'dbname='    . $this->getDatabase();

        return implode(' ', $parameters);
    }