private void loadQueueHolder(boolean insert) {
    DataIterator<T> dataIterator = insert ? insertDataIterator : deleteDataIterator;
    QueueHolder<T> holder = insert ? insertHolder : deleteHolder;
    if (dataIterator.hasNext() && holder.isEmpty()) {
      T next = dataIterator.next();
      long nextOffset = dataIterator.currentMixedFormatFileOffset();
      ChangeAction changeAction = insert ? INSERT : DELETE;
      holder.put(next, changeAction, nextOffset);
    }
  }
This is a change log data iterator that replays the change log data appended to mixed-format
change table with ordered.
amoro-format-mixed/amoro-mixed-flink/amoro-mixed-flink-common/src/main/java/org/apache/amoro/flink/read/source/ChangeLogDataIterator.java