private CloseableIterator<T> openTaskIterator(MixedFileScanTask scanTask) {
    return fileScanTaskReader.open(scanTask);
  }
Updates the current iterator field to ensure that the current Iterator is not exhausted.
amoro-format-mixed/amoro-mixed-flink/amoro-mixed-flink-common/src/main/java/org/apache/amoro/flink/read/source/DataIterator.java