private void skipDeletedDoc(DocValuesFieldUpdates.Iterator[] updatesIters, int deletedDoc) {
    for (DocValuesFieldUpdates.Iterator iter : updatesIters) {
      if (iter.doc() == deletedDoc) {
        iter.nextDoc();
      }
      // when entering the method, all iterators must already be beyond the
      // deleted document, or right on it, in which case we advance them over
      // and they must be beyond it now.
      assert iter.doc() > deletedDoc : "updateDoc=" + iter.doc() + " deletedDoc=" + deletedDoc;
    }
  }