protected void marshall(BsonDocumentBuilder builder) {
    if (errorDesc == null) {
      assert error.equals(ErrorCode.OK);
      builder.appendNull(ERR_FIELD_NAME);
    } else {
      builder.append(ERR_FIELD_NAME, errorDesc);
      builder.append(CODE_FIELD_NAME, error.getErrorCode());
    }
    builder.append(N_FIELD_NAME, getN());

    if (replInfo != null) {
      replInfo.marshall(builder);
    }
    if (shardInfo != null) {
      shardInfo.marshall(builder);
    }
  }