anchor.diff:  -spec approximate_size(Shard :: string()) ->
       {ok, Size :: pos_integer()} | {error, Reason :: term()}.
   approximate_size(Shard) ->
  -    ServerRef = enterdb_ns:get(Shard),
  -    gen_server:call(ServerRef, approximate_size).
  +    ServerRef = enterdb_ns:get({Shard, reader}),
  +    call(ServerRef, approximate_size).
   
   %%--------------------------------------------------------------------
   %% @doc
  
positive.code:     {error, Reason :: term()}.
  read_range_binary(Shard, Range, Chunk) ->
      ServerRef = enterdb_ns:get(Shard),
      gen_server:call(ServerRef, {read_range, Range, Chunk, binary}).
  
  %%--------------------------------------------------------------------
  %% @doc
  
negative.code:     ok | {error, Reason :: term()}.
  set_ttl(Shard, TTL) ->
      Pid = enterdb_ns:get(Shard),
      call(Pid, {set_ttl, TTL}).
  
  %%--------------------------------------------------------------------
  %% @private
  