PHP實例
public function database($params = '', $return = FALSE, $active_record = NULL)
{
  $CI =& get_instance();
  if (class_exists('CI_DB') AND $return == FALSE AND $active_record == NULL AND isset($CI->db) AND is_object($CI->db)) {
    return FALSE;
  }
  if(file_exists(APPPATH.'core/database/DB.php')) {
    require_once(APPPATH.'core/database/DB.php');
  } else {
    require_once(BASEPATH.'database/DB.php');
  }
  if ($return === TRUE) {
    return DB($params, $active_record);
  }
  $CI->db = '';
  $CI->db =& DB($params, $active_record);
}
/* End of file MY_Loader.php */
/* Location: ./application/core/MY_Loader.php */

PHP實例
//DB_driver.php為所有驅動方式的父類,最終執行查詢的辦法在該文件中
//第一處修改為判斷自定義的DB_driver.php是否存在,存在則引入
if(file_exists(APPPATH.'core/database/DB_driver.php')) {
  require_once(APPPATH.'core/database/DB_driver.php');
} else {
  require_once(BASEPATH.'database/DB_driver.php');
}
//第二處 $params['dbdriver'].'_driver.php' 該文件可不調整,實際未修改該文件,為了方便調試也加了
//mysql驅動對應system/database/drivers/mysql/mysql_driver.php,mysql的最后執行辦法在這里,
//包括數據庫打開和關閉、查詢等,可以該文件增加相應日志查看讀寫分離是否有效
if(file_exists(APPPATH.'core/database/drivers/'.$params['dbdriver'].'/'.$params['dbdriver'].'_driver.php')) {
  require_once(APPPATH.'core/database/drivers/'.$params['dbdriver'].'/'.$params['dbdriver'].'_driver.php');
} else {
  require_once(BASEPATH.'database/drivers/'.$params['dbdriver'].'/'.$params['dbdriver'].'_driver.php');
}
//將當前group name賦值給param,方便判斷
$params['group_name'] = $active_group;
 
/* End of file DB.php */
/* Location: ./application/core/database/DB.php */

PHP實例
if ($DB->autoinit == TRUE)
{
  $DB->initialize();
}

PHP實例
//增加屬性,表示當前組
var $active_group;
//增加屬性,使用強制使用主庫
var $db_force_master;
//該辦法為執行查詢的必經之地,我們可以在這里根據類型判斷使用哪個鏈接.
function simple_query($sql)
{
  //load_db_proxy_setting辦法這里寫在helper中,也可以直接寫在該類中,寫在helper中則需要在自動加載中加載該helper
  //該辦法的作用是根據當前鏈接group name 和sql讀寫類型,以及是否強制使用主庫判斷使用哪個鏈接.使用主庫 OR 重庫?
  //主重庫的負載均衡,單點故障都可以在這里考慮.也就是根據3個參數返回一個可用的配置數組.
  $proxy_setting = load_db_proxy_setting($this->group_name, $this->is_write_type($sql), $this->db_force_master);
  if(is_array($proxy_setting) && ! empty($proxy_setting)) {
    $proxy_setting_key = key($proxy_setting);
    $this->group_name = $proxy_setting_key;
    //將當前配置重新賦值給類的屬性,如果database.php配置的是DSN字符串,則需要在load_db_proxy_setting中做處理
    foreach($proxy_setting[$proxy_setting_key] as $key => $val) {
      $this->$key = $val;
    }
    //定義鏈接ID為conn_前綴
    $proxy_conn_id = 'conn_'.$proxy_setting_key;
    $CI = & get_instance();
    //賦值給CI超級對象或者直接從CI超級對象中讀取
    if(isset($CI->$proxy_conn_id) && is_resource($CI->$proxy_conn_id)) {
      $this->conn_id = $CI->$proxy_conn_id;
    } else {
      $this->conn_id = false;
      $this->initialize();
      $CI->$proxy_conn_id = $this->conn_id;
    }
    //強制只一次有效,下次查詢失效,防止一直強制主庫
    $this->reset_force_master();
  }
  if ( ! $this->conn_id)
  {
    $this->initialize();
  }
  return $this->_execute($sql);
}
//某些情況會強制使用主庫,先執行該辦法即可
public function force_master()
{
  $this->db_force_master = TRUE;
}
public function reset_force_master()
{
  $this->db_force_master = FALSE;
}
/* End of file DB_driver.php */
/* Location: ./application/core/database/DB_driver.php */

PHP實例
class MY_Controller extends CI_Controller 
{
  public function __construct() 
  {
    parent::__construct();
    $this->load->service('common/helper_service', NULL, 'helper');
    //下面這段為關閉CI超級對象中的數據庫對象和數據庫鏈接,db的對象Codeigniter.php中會關閉
    register_shutdown_function(function(){
      foreach(get_object_vars($this) as $key => $val) {
        if(substr($key, 0, 3) == 'db_' && is_object($this->{$key}) && method_exists($this->{$key}, 'close')) {
          $this->{$key}->close();
        }
        if(substr($key, 0, 5) == 'conn_' && is_resource($this->{$key})) {
          $this->db->_close($val);
          unset($this->{$key});
        }
      }
    });
  }
}
/* End of file MY_Controller.php */
/* Location: ./application/core/MY_Controller.php */

PHP實例
public function __construct($group_name = '')
{
  parent::__construct();
  $this->initDb($group_name);
}
private function initDb($group_name = '')
{
  $db_conn_name = $this->getDbName($group_name);
  $CI = & get_instance();
  if(isset($CI->{$db_conn_name}) && is_object($CI->{$db_conn_name})) {
    $this->db = $CI->{$db_conn_name};
  } else {
    $CI->{$db_conn_name} = $this->db = $this->load->database($group_name, TRUE);
  }
}
private function getDbName($group_name = '')
{
  if($group_name == '') {
    $db_conn_name = 'db';
  } else {
    $db_conn_name = 'db_'.$group_name;
  }
  return $db_conn_name;
}
/* End of file MY_Model.php */
/* Location: ./application/core/MY_Model.php */

PHP實例
$_master_slave_relation = array(
  'default_master' => array('default_slave1', 'default_slave2', 'default_slave3'),
);
/* End of file database.php */
/* Location: ./application/config/database.php */