presto-main/src/main/java/io/prestosql/sql/planner/SchedulingOrderVisitor.java/SchedulingOrderVisitor/scheduleOrder
class SchedulingOrderVisitor:    public static List<PlanNodeId> scheduleOrder(PlanNode root)
    {
        ImmutableList.Builder<PlanNodeId> schedulingOrder = ImmutableList.builder();
        root.accept(new Visitor(schedulingOrder::add), null);
        return schedulingOrder.build();
    }