vr.order = order;
    Relation getGroupbySubnodeRelation() {        if (groupby == null) {            throw new RuntimeException("getGroupbySubnodeRelation called on non-group-by relation");        }        Relation vr = new Relation(this);        vr.order = order;        vr.prototype = groupbyPrototype;        vr.filter = filter;        vr.constraints = constraints;        vr.addConstraint(new Constraint(null, groupby, true));        vr.aggressiveLoading = aggressiveLoading;        vr.aggressiveCaching = aggressiveCaching;        return vr;    }