anchor.diff:  %% move to another map.
   update_all_state(OldValue, NewValue, State) ->
   	State.
  +
   
   get_map_by_id(Id, State) ->
   	case dict:find(Id, State#state.by_id) of
  
positive.code: 	Info2_1_1 = #info{id=2, map=m1, x=101, y=101},
  	Info2_2_2 = #info{id=2, map=m2, x=102, y=101},
  	set_info(1, Info1_1_1),
  	set_info(1, Info1_1_2),
  	set_info(2, Info2_1_1).
  
  get_info(Id) ->
  	{ok, V} = gen_server:call(?MODULE, {get_info, Id}) ,
  
negative.code: 	#state{by_id = ByIdDict, by_map = ByMapDict}.
  
  %% move in same map.
  	%%when is_record(OldValue, info),
  	%%	is_record(NewValue, info),
  	%%	OldValue#info.map == NewValue#info.map ->
  update_all_state(OldValue, NewValue, State) ->
  
  	#state{by_id = ByIdDict, by_map = ByMapDict} = State,
  	Id = NewValue#info.id,
  