anchor.diff:                      case Filter(Key) of
                           true ->
                               BufferMod:add(Key, Buffer);
  -                        false ->
  -                            Buffer
  -                    end;
  -                _ ->
  -                    Buffer
  -            end
  -    end;
  -fold_fun({keys, RecoverTsFun}, BufferMod, Filter, {Bucket, Index, N, NumPartitions}) ->
  -    fun(_, Key, Buffer) ->
  -            Hash = riak_core_util:chash_key({Bucket, Key}),
  -            case riak_core_ring:future_index(Hash, Index, N, NumPartitions, NumPartitions) of
  -                Index ->
  -                    CompoundKey = RecoverTsFun(Key),
  -                    case Filter(CompoundKey) of
  -                        true ->
  -                            BufferMod:add(CompoundKey, Buffer);
                           false ->
                               Buffer
                       end;
  
positive.code:                     Buffer
              end
      end;
  fold_fun({keys, RecoverTsFun}, BufferMod, Filter, undefined) ->
      fun(_, Key, Buffer) ->
              CompoundKey = RecoverTsFun(Key),
              case Filter(CompoundKey) of
                  true ->
                      BufferMod:add(CompoundKey, Buffer);
                  false ->
                      Buffer
              end
      end;
  fold_fun(keys, BufferMod, Filter, {Bucket, Index, N, NumPartitions}) ->
      fun(_, Key, Buffer) ->
              Hash = riak_core_util:chash_key({Bucket, Key}),
  
negative.code:     BufferSize = proplists:get_value(buffer_size, Opts0, DefaultBufSz),
      Buffer = BufferMod:new(BufferSize, ResultFun),
      Extras = fold_extras_keys(Index, Bucket),
      FoldFunSelector = keys,
      FoldFun = fold_fun(FoldFunSelector, BufferMod, Filter, Extras),
      FinishFun = finish_fun(BufferMod, Sender),
  