vr.groupbyorder = groupbyorder; vr.groupbyprototype = groupbyprototype;
vr.groupbyOrder = groupbyOrder; vr.groupbyPrototype = groupbyPrototype;
    Relation getVirtualPropertyRelation () {	if (!virtual)	    throw new RuntimeException ("getVirtualPropertyRelation called on non-virtual relation");	Relation vr = new Relation (this);	vr.groupby = groupby;	vr.groupbyorder = groupbyorder;	vr.groupbyprototype = groupbyprototype;	vr.order = order;	vr.filter = filter;	vr.maxSize = maxSize;	vr.constraints = constraints;	return vr;    }