protected function _getColumnProperty($column_name)
 {
     if (!($property_name = B2DB::getCachedColumnClassProperty($column_name, get_class($this)))) {
         $property = explode('.', $column_name);
         $property_name = "_" . strtolower($property[1]);
         B2DB::addCachedColumnClassProperty($column_name, get_class($this), $property_name);
     }
     return $property_name;
 }