if( empty($post['sale_id']) || 
  (!empty($post['sale_id']) && null == ( $row =  $this->_model->find($post['sale_id']) )) ||
  (!empty($post['sale_id']) && null == ( $row =  $this->_model->fetch(" tag = '".$post['tag']."' AND item_id = '".$post['item_id']."' AND visit_id ='".$post['visit_id']."'") ))
) $row = $this->_model->fetchNew();