protected function lightDelete()
     {
         $now = Time::current();
         $key = $this->getPKvalue();
         //
         $sql = 'update '.$this->DBtable." set deleted_at='".$now."' where ".$this->keyName." = '".$key."' ";
         if (Database::exec($sql)) {
             $this->clean();
             $this->deleted_at = $now;
         }
     }