/**
* Create new unique pk as md5 hash and puts it to field root_id if this is
* not a comment.
* if pk consists of multiple columns, false is returned
* @return boolean|string
*/
function getNewId()
{
$id = parent::getNewId();
if (!$this['root_id']) {
$this['root_id'] = $id;
}
return $id;
}
