private void lockKeyedProperty(TitanProperty prop, StoreMutator mutator) throws StorageException {
   TitanKey pt = prop.getPropertyKey();
   assert pt.isSimple();
   if (pt.hasIndex() && pt.isUnique()) {
     if (prop.isNew()) {
       mutator.acquireIndexLock(getIndexKey(prop.getAttribute()), getKeyedIndexColumn(pt), null);
     } else {
       assert prop.isRemoved();
       mutator.acquireIndexLock(
           getIndexKey(prop.getAttribute()), getKeyedIndexColumn(pt), getIndexValue(prop));
     }
   }
 }