anchor.diff:           determine_data_root/0,
            exchange_bucket/4,
            exchange_segment/3,
  +         estimate_keys/1,
  +         estimate_keys/2,
            hash_index_data/1,
            hash_object/2,
            update/2,
  
positive.code:     State2 = State#state{expired=true},
      lager:info("Manually expired tree: ~p", [State#state.index]),
      {reply, ok, State2};
  
  handle_call(_Request, _From, State) ->
      Reply = ok,
  
negative.code: %% @doc Expire the specified index_hashtree
  expire(Tree) ->
      gen_server:call(Tree, expire, infinity).
  
  %% @doc Estimate total number of keys in index_hashtree
  estimate_keys(Tree) ->
      gen_server:call(Tree, estimate_keys, infinity).
  
  %% @doc Estimate total number of keys in index_hashtree
  estimate_keys(Tree, IndexN) ->
      gen_server:call(Tree, {estimate_keys, IndexN}, infinity).
  
  %%%===================================================================
  %%% gen_server callbacks
  