code: public function refresh()
      {
          $this->_totalCount = null;
          $this->_models = null;
          $this->_keys = null;
      }
docs: Refreshes the data provider.
  After calling this method, if [[getModels()]], [[getKeys()]] or [[getTotalCount()]] is called again,
  they will re-execute the query and return the latest data available.