private void addIndexEntry(TitanProperty prop, StoreMutator mutator) throws StorageException {
   TitanKey pt = prop.getPropertyKey();
   assert pt.isSimple();
   if (pt.hasIndex()) {
     if (pt.isUnique()) {
       mutator.mutateIndex(
           getIndexKey(prop.getAttribute()),
           Lists.newArrayList(new Entry(getKeyedIndexColumn(pt), getIndexValue(prop))),
           null);
     } else {
       mutator.mutateIndex(
           getIndexKey(prop.getAttribute()),
           Lists.newArrayList(new Entry(getIndexColumn(pt, prop.getID()), getIndexValue(prop))),
           null);
     }
   }
 }