Nette\Database\Connection::connect PHP Method

    public function connect()
    {
        if ($this->pdo) {
            return;
        }
        try {
            $this->pdo = new PDO($this->params[0], $this->params[1], $this->params[2], $this->options);
            $this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        } catch (PDOException $e) {
            throw ConnectionException::from($e);
        }
        $class = empty($this->options['driverClass']) ? 'Nette\\Database\\Drivers\\' . ucfirst(str_replace('sql', 'Sql', $this->pdo->getAttribute(PDO::ATTR_DRIVER_NAME))) . 'Driver' : $this->options['driverClass'];
        $this->driver = new $class($this, $this->options);
        $this->preprocessor = new SqlPreprocessor($this);
        $this->onConnect($this);
    }

 /**
  * @param  string  statement
  * @param  array
  * @return ResultSet
  */
 public function queryArgs($statement, array $params)
 {
     $this->connection->connect();
     if ($params) {
         if (!$this->preprocessor) {
             $this->preprocessor = new SqlPreprocessor($this->connection);
         }
         array_unshift($params, $statement);
         list($statement, $params) = $this->preprocessor->process($params);
     }
     try {
         $result = new ResultSet($this->connection, $statement, $params);
     } catch (\PDOException $e) {
         $e->queryString = $statement;
         $this->connection->onQuery($this->connection, $e);
         throw $e;
     }
     $this->connection->onQuery($this->connection, $result);
     return $result;
 }