anchor.diff:  
   -include("antidote.hrl").
   
  +-define(CLAIMED, claimed).
  +
   %% API
   -export([u_index/4,
            read_u_index/3,
  
positive.code:     ok = pvc:update_keys(Updates, TxId),
      gen_fsm:sync_send_event(Pid, {pvc_index, Updates}, ?OP_TIMEOUT).
  
  %% TODO(borja): Handle non-binary data
  make_u_index_key(IndexName, IndexValue) ->
      <<IndexName/binary, IndexValue/binary>>.
  
negative.code: index(IndexName, IndexValue, RefKey, TxId) ->
      RootKey = make_u_index_key(IndexName, IndexValue),
      IndexKey = make_index_key(IndexName, IndexValue, RefKey),
      Updates = case claimed_index(RootKey, TxId) of
          false ->
              [{RootKey, ?CLAIMED}, {IndexKey, RefKey}];
  
          true ->
              [{IndexKey, RefKey}]
      end,
      update_indices(Updates, TxId).
  