private static void addResourceIdentifierSet(
      SolrInputDocument doc, Collection<DcsResourceIdentifier> set) {
    if (set == null || set.size() == 0) {
      return;
    }

    for (DcsResourceIdentifier id : set) {
      setadd(doc, ResourceIdentifierField.AUTHORITY, id.getAuthorityId());
      setadd(doc, ResourceIdentifierField.TYPE, id.getTypeId());
      setadd(doc, ResourceIdentifierField.VALUE, id.getIdValue());
    }
  }