CodeIgniter で複数のデータベース接続を管理するにはどうすればよいですか?

$db['default']['hostname'] = 'your_hostname';
$db['default']['username'] = 'your_username';
$db['default']['password'] = 'your_password';
$db['default']['database'] = 'your_database';
$db['default']['dbdriver'] = 'mysql';
$db['default']['dbprefix'] = '';
$db['default']['pconnect'] = TRUE;
$db['default']['db_debug'] = FALSE;
$db['default']['cache_on'] = FALSE;
$db['default']['cachedir'] = '';
$db['default']['char_set'] = 'utf8';
$db['default']['dbcollat'] = 'utf8_general_ci';

$db['otherdb']['hostname'] = 'other_hostname';
$db['otherdb']['username'] = 'other_username';
$db['otherdb']['password'] = 'other_password';
$db['otherdb']['database'] = 'other_database';
$db['otherdb']['dbdriver'] = 'mysql';
$db['otherdb']['dbprefix'] = '';
$db['otherdb']['pconnect'] = TRUE;
$db['otherdb']['db_debug'] = FALSE;
$db['otherdb']['cache_on'] = FALSE;
$db['otherdb']['cachedir'] = '';
$db['otherdb']['char_set'] = 'utf8';
$db['otherdb']['dbcollat'] = 'utf8_general_ci';

function my_model_method()
{
  $otherdb = $this->load->database('otherdb', TRUE); // the TRUE paramater tells CI that you'd like to return the database object.

  $query = $otherdb->select('first_name, last_name')->get('person');
  var_dump($query);
}