@Override
  public boolean hasNext() {
    loadQueueHolder(false);
    loadQueueHolder(true);

    return deleteHolder.isNotEmpty() || insertHolder.isNotEmpty();
  }
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