anchor.diff:      toke_drv:delete(DB, ?IN(Key)),
       State.
   
  -%% @doc Returns the name of the DB specified in new/1.
  +%% @doc Returns the name of the DB specified in @see new/1.
   -spec get_name(DB::db()) -> nonempty_string().
   get_name({_DB, FileName}) ->
       FileName.
  
positive.code:                                  end
                           end, [], DB),
      CutData = lists:sublist(Data, MaxNum),
      lists:foldr(Fun, Acc, CutData).
  
  is_in({element, Key}, OtherKey) -> Key =:= OtherKey;
  
negative.code:                                       {Max, AccIn}
                                end
                        end, {MaxNum, []}, DB),
      %% see HINT in foldl/3
      lists:foldl(Fun, Acc, Data).
  
  %% @doc makes a foldr over the whole dataset.
  %%      Returns a potentially larger-than-memory dataset. Use with care.
  -spec foldr(DB::db(), Fun::fun((entry(), AccIn::A) -> AccOut::A), Acc0::A) -> Acc1::A.
  foldr({DB, _FileName}, Fun, Acc) ->
      Data = toke_drv:fold(fun(_Key, Entry, AccIn) ->
                                   [?OUT(Entry) | AccIn]
                           end, [], DB),
      %% see HINT in foldl/3
      lists:foldr(Fun, Acc, Data).
  
  %% @equiv foldr(DB, Fun, Acc0, Interval, get_load(DB))
  %% @doc   Returns a potentially larger-than-memory dataset. Use with care.
  -spec foldr(DB::db(), Fun::fun((entry(), AccIn::A) -> AccOut::A), Acc0::A,
                                 Interval::db_backend_beh:interval()) -> Acc1::A.
  foldr({DB, _FileName}, Fun, Acc, Interval) ->
  