reduce_stream_kp_node(Bt, Dir, NodeList, KeyStart, KeyEnd,
                        GroupedKey, GroupedKVsAcc, GroupedRedsAcc,
                        KeyGroupFun, Fun, Acc) ->
    Nodes =
    case KeyStart of
    undefined ->
        NodeList;
    _ ->
        lists:dropwhile(
            fun({Key,_}) ->
                less(Bt, Key, KeyStart)
            end, NodeList)
    end,
    NodesInRange =
    case KeyEnd of
    undefined ->
        Nodes;
    _ ->
        {InRange, MaybeInRange} = lists:splitwith(
            fun({Key,_}) ->
                less(Bt, Key, KeyEnd)
            end, Nodes),
        InRange ++ case MaybeInRange of [] -> []; [FirstMaybe|_] -> [FirstMaybe] end
    end,
    reduce_stream_kp_node2(Bt, Dir, adjust_dir(Dir, NodesInRange), KeyStart, KeyEnd,
        GroupedKey, GroupedKVsAcc, GroupedRedsAcc, KeyGroupFun, Fun, Acc).


====================
reduce_stream_kp_node(Bt, Dir, NodeList, KeyStart, KeyEnd,
                        GroupedKey, GroupedKVsAcc, GroupedRedsAcc,
                        KeyGroupFun, Fun, Acc) ->
    Nodes =
        case KeyStart of
            undefined ->
                NodeList;
            _ ->
                lists:dropwhile(
                  fun({Key,_}) ->
                          less(Bt, Key, KeyStart)
                  end, NodeList)
        end,
    NodesInRange =
        case KeyEnd of
            undefined ->
                Nodes;
            _ ->
                {InRange, MaybeInRange} = lists:splitwith(
                                            fun({Key,_}) ->
                                                    less(Bt, Key, KeyEnd)
                                            end, Nodes),
                InRange ++ case MaybeInRange of [] -> []; [FirstMaybe|_] -> [FirstMaybe] end
        end,
    reduce_stream_kp_node2(Bt, Dir, adjust_dir(Dir, NodesInRange), KeyStart, KeyEnd,
        GroupedKey, GroupedKVsAcc, GroupedRedsAcc, KeyGroupFun, Fun, Acc).