问CodeIgniter DB Forge添加引擎和表中的唯一键

EN

$sql = "DROP TABLE IF EXISTS `plugins`;
                  CREATE TABLE `plugins` (
                  `plugin_id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
                  `plugin_system_name` varchar(255) NOT NULL,
                  `plugin_name` varchar(255) NOT NULL,
                  `plugin_uri` varchar(120) DEFAULT NULL,
                  `plugin_version` varchar(30) NOT NULL,
                  `plugin_description` text,
                  `plugin_author` varchar(120) DEFAULT NULL,
                  `plugin_author_uri` varchar(120) DEFAULT NULL,
                  `plugin_data` longtext,
                   PRIMARY KEY (`plugin_id`),
                   UNIQUE KEY `plugin_index` (`plugin_system_name`) USING BTREE
                   ) ENGINE=MyISAM AUTO_INCREMENT=9 DEFAULT CHARSET=latin1; ";
$this->db->query($sql);

<?php  if (! defined('BASEPATH')) exit('No direct script access allowed');
/**
 * Sparks
 *
 * An open source application development framework for PHP 5.1.6 or newer
 *
 * @package  CodeIgniter
 * @author  CodeIgniter Reactor Dev Team
 * @author      Kenny Katzgrau <katzgrau@gmail.com>
 * @since  CodeIgniter Version 1.0
 * @filesource
 */

/**
 * Loader Class
 *
 * Loads views and files
 *
 * @package  CodeIgniter
 * @subpackage Libraries
 * @author  CodeIgniter Reactor Dev Team
 * @author      Kenny Katzgrau <katzgrau@gmail.com>
 * @category Loader
 * @link  http://ellislab.com/codeigniter/user-guide/libraries/loader.html
 */
class MY_Loader extends CI_Loader
{
   ...

 // --------------------------------------------------------------------

 /**
  * Load the Database Forge Class
  *
  * @return string
  */
 public function dbforge()
 {
  if ( ! class_exists('CI_DB'))
  {
   $this->database();
  }

  $CI =& get_instance();

  require_once(BASEPATH.'database/DB_forge.php');
  require_once(BASEPATH.'database/drivers/'.$CI->db->dbdriver.'/'.$CI->db->dbdriver.'_forge.php');
  /* Look for overload files in the /application/core folder */
  if (file_exists(BASEPATH.'../'.APPPATH.'core/MY_CI_DB_'.$CI->db->dbdriver.'_forge.php')) {
   require_once(BASEPATH.'../'.APPPATH.'core/MY_CI_DB_'.$CI->db->dbdriver.'_forge.php');
   $class = 'MY_CI_DB_'.$CI->db->dbdriver.'_forge';
  } else {  
   $class = 'CI_DB_'.$CI->db->dbdriver.'_forge';
  }

  $CI->dbforge = new $class();
 } 
} 

<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');

/**
 * MySQL Forge Class Force MYISAM
 *
 * @category Database
 * @author 
 * @link 
 */
class MY_CI_DB_mysql_forge extends CI_DB_mysql_forge {
 // --------------------------------------------------------------------


 /**
  * Create Table
  *
  * @access private
  * @param string the table name
  * @param mixed the fields
  * @param mixed primary key(s)
  * @param mixed key(s)
  * @param boolean should 'IF NOT EXISTS' be added to the SQL
  * @return bool
  */
 function _create_table($table, $fields, $primary_keys, $keys, $if_not_exists)
 {

  $sql = 'CREATE TABLE ';

  if ($if_not_exists === TRUE)
  {
   $sql .= 'IF NOT EXISTS ';
  }

  $sql .= $this->db->_escape_identifiers($table)." (";

  $sql .= $this->_process_fields($fields);

  if (count($primary_keys) > 0)
  {
   $key_name = $this->db->_protect_identifiers(implode('_', $primary_keys));
   $primary_keys = $this->db->_protect_identifiers($primary_keys);
   $sql .= ",\n\tPRIMARY KEY ".$key_name." (" . implode(', ', $primary_keys) . ")";
  }

  if (is_array($keys) && count($keys) > 0)
  {
   foreach ($keys as $key)
   {
    if (is_array($key))
    {
     $key_name = $this->db->_protect_identifiers(implode('_', $key));
     $key = $this->db->_protect_identifiers($key);
    }
    else
    {
     $key_name = $this->db->_protect_identifiers($key);
     $key = array($key_name);
    }

    $sql .= ",\n\tKEY {$key_name} (" . implode(', ', $key) . ")";
   }
  }

  $sql .= "\n) ENGINE=MYISAM DEFAULT CHARACTER SET {$this->db->char_set} COLLATE {$this->db->dbcollat};";

  return $sql;
 }
}