@Override
  public void serialize(DataOutputStream stream) throws IOException {
    stream.writeShort(ProcedureType.ALTER_TOPIC_PROCEDURE.getTypeCode());
    super.serialize(stream);

    ReadWriteIOUtils.write(updatedTopicMeta != null, stream);
    if (updatedTopicMeta != null) {
      updatedTopicMeta.serialize(stream);
    }

    ReadWriteIOUtils.write(existedTopicMeta != null, stream);
    if (existedTopicMeta != null) {
      existedTopicMeta.serialize(stream);
    }
  }
This should be called after {@link #executeFromValidate}.
iotdb-core/confignode/src/main/java/org/apache/iotdb/confignode/procedure/impl/subscription/topic/AlterTopicProcedure.java