anchor.diff:      case proplists:get_value(bucket, Opts) of
           undefined ->
               fold_all(fold_objects, FoldObjectsFun, Acc, Opts, State,
  -                    fun default_backend_filter/4);
  +                    fun default_backend_filter/5);
           Bucket ->
               fold_in_bucket(Bucket, fold_objects, FoldObjectsFun, Acc, Opts, State)
       end.
  
positive.code:     case proplists:get_value(bucket, Opts) of
          undefined ->
              fold_all(fold_keys, FoldKeysFun, Acc, Opts, State,
                      fun default_backend_filter/4);
          Bucket ->
              fold_in_bucket(Bucket, fold_keys, FoldKeysFun, Acc, Opts, State)
      end.
  
negative.code:                    state()) -> {ok, any()} | {async, fun()} | {error, term()}.
  fold_buckets(FoldBucketsFun, Acc, Opts, State) ->
      fold_all(fold_buckets, FoldBucketsFun, Acc, Opts, State,
               fun default_backend_filter/5).
  
  %% @doc Fold only over index data in the backend, for all buckets.
  fold_indexes(FoldIndexFun, Acc, Opts, State) ->
      fold_all(fold_indexes, FoldIndexFun, Acc, Opts, State,
              fun indexes_filter/5).
  
  %% @doc Fold over all the keys for one or all buckets.
  -spec fold_keys(riak_kv_backend:fold_keys_fun(),
  