private function connect()
    {
        if (!$this->isConnected) {
            parent::__construct(
                $this->dsn,
                $this->server->getUsername(),
                $this->server->getPassword(),
                $this->driverOptions
            );
            parent::setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            parent::setAttribute(
                PDO::ATTR_STATEMENT_CLASS,
                [__NAMESPACE__ . '\\' . self::PDO_STATEMENT_CLASS, [$this]]
            );

            $this->isConnected = true;
        }
    }