未为已配置的数据库启用查询生成器

I am using ci version 3.0.4. I try to fix the error but didnt find solution So I am posting here Please help. Is there any wrong in my configuration of config, constant,or controllers files.? Is there any wrong in my configuration of config, constant,or controllers files.

**Error:** 

An uncaught Exception was encountered

Type: Exception

Message: Query Builder not enabled for the configured database. Aborting.

Filename: G:\xampp\software\htdocs\24mehta\system\libraries\Session\drivers\Session_database_driver.php

Line Number: 90

**Adminx controller:**

class Adminx extends CI_Controller {

    function __construct() {
        parent::__construct();

        $this->load->module('login');

        $this->load->helper('form');
        $this->output->enable_profiler(ENABLE_PROFILER);
        $this->load->model('Page_DB_Interaction', 'page_db_interaction');
        $login = new Login();
        if (!$login->_is_logged_in()) {
            $citer = &get_instance();
            $url_page = $citer->uri->segment(1);
            $this->session->set_userdata('url_page', $url_page);
            $this->session->set_userdata('login_page', 'backend');
            redirect('login');
        }
    }

**Autoload file:**
$autoload['libraries'] = array('database');
$autoload['drivers'] = array('session');

**login controller**

class Login extends CI_Controller {

    function __construct() {

        parent::__construct();

        $this->load->helper('directory');
        $this->load->helper('cookie');
        $this->load->model('Global_model', 'gm');


    }

**config file:**
$config['sess_driver'] = 'database';
$config['sess_cookie_name'] = 'easfsession';
$config['sess_expiration'] = 7200;
$config['sess_save_path'] = 'NULL';
$config['sess_match_ip'] = FALSE;
$config['sess_time_to_update'] = 300;
$config['sess_regenerate_destroy'] = FALSE;

I am using ci version '3.0.4'

Check the file /application/config/database.php and make sure that $query_builder = TRUE; My guess it's currently set to FALSE.

I also suggest that the session be loaded as a library and not a driver.

$autoload['libraries'] = array('database', 'session');
//remove this line
//$autoload['drivers'] = array('session'); 

In the session config use this

$config['sess_save_path'] = 'ci_sessions'; //assumes `ci_sessions` is the table name you are using