anchor.diff:          [{Key, {Value, WriteLock, ReadLock, Version}}] ->
               ?ETS:insert(DB, {Key, {Value, WriteLock, ReadLock - 1, Version}}),
               {DB, ok};
  -        [] ->
  -            {DB, failed}
  +        [] -> {DB, failed}
       end.
   
   %% @doc get the locks and version of a key
  
positive.code: -spec(get_range/3 :: (db(), key(), key()) -> [{key(), value()}]).
  get_range(DB, From, To) ->
      F = fun ({Key, {Value, _, _, _}}, Data) ->
                  case util:is_between(From, Key, To) andalso Value =/= empty_val of
                      true ->
                          [{Key, Value} | Data];
                      false ->
                          Data
                  end
          end,
      ?ETS:foldl(F, [], DB).
  
negative.code:             {DB, ok};
          [{Key, {_Value, false, _ReadLock, _Version}}] ->
              {DB, failed};
          [] -> {DB, failed}
      end.
  
  %% @doc sets a read lock on a key
  