isUnique validation

Using isUnique validation of Cakephp, need to attach Mongodb.SqlCompatible behavior before saving. Here is sample code of controller::add() action.

  public function add() {
    if (!empty($this->data)) {
      $this->Geo->create();

      //need to attach behavior
      $this->Geo->Behaviors->attach('Mongodb.SqlCompatible');

      if ($this->Geo->save($this->data)) {
        $this->flash(__('Geo saved.', true), array('action' => 'index'));
      } else {
      }
    }
  }

Here is Model::validate setting.

  public $validate = array(
    'title' => array(
      'rule' => 'isUnique',
      'required' => false
    ),
  );