anchor.diff:  %%          data is to be retrieved.
   -spec foldr_helper(DB::db(), Fun::fun((Key::key(), AccIn::A) -> AccOut::A), Acc0::A,
                                  Intervall::db_backend_beh:interval(), MaxNum::integer()) -> Acc1::A.
  -foldr_helper({DB, _FileName}, Fun, Acc, Interval, MaxNum) ->
  +foldr_helper({DB, _DBName}, Fun, Acc, Interval, MaxNum) ->
       %% first only retrieve keys so we don't have to load the whole db into memory
       Keys = get_all_keys(DB, Interval, -1),
       CutData = case MaxNum of
  
positive.code:     end,
      case toke_drv:new(DB) of
          ok ->
              case toke_drv:open(DB, FileName, TokeOptions) of
                  ok -> {DB, FileName};
                  Error2 ->
                      log:log(error, "[ Node ~w:db_toke ] ~.0p", [self(), Error2]),
                      erlang:error({toke_failed, Error2})
  
negative.code: 
  %% @doc Closes the DB named DBName
  -spec close(DB::db()) -> true.
  close({DB, _DBName}) ->
      toke_drv:close(DB),
      toke_drv:delete(DB),
      toke_drv:stop(DB).
  
  %% @doc Closes and deletes the DB named DBName
  -spec close_and_delete(DB::db()) -> true.
  close_and_delete({_DB, DBName} = State) ->
      close(State),
      FileName = [config:read(db_directory), "/", atom_to_list(node()), "/",
                  DBName, ".tch"],
      case file:delete(FileName) of
          ok -> ok;
          {error, Reason} ->
  