private void requestSplit(Collection<String> finishedSplitIds) {
    context.sendSourceEventToCoordinator(new SplitRequestEvent(finishedSplitIds));
  }
SourceEvents may be received before this#pollNext.
amoro-format-mixed/amoro-mixed-flink/amoro-mixed-flink-common/src/main/java/org/apache/amoro/flink/read/hybrid/reader/MixedFormatSourceReader.java