public synchronized void updatePendingDataBlockInfo(
      int startSequenceId, List<Long> dataBlockSizes) {
    if (LOGGER.isDebugEnabled()) {
      LOGGER.debug(
          "[ReceiveNewTsBlockNotification] [{}, {}), each size is: {}",
          startSequenceId,
          startSequenceId + dataBlockSizes.size(),
          dataBlockSizes);
    }
    for (int i = 0; i < dataBlockSizes.size(); i++) {
      sequenceIdToDataBlockSize.put(i + startSequenceId, dataBlockSizes.get(i));
    }
    if (canGetTsBlockFromRemote) {
      trySubmitGetDataBlocksTask();
    }
  }
this is set to true after calling isBlocked() at least once which indicates that this
SourceHandle needs to output data.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/exchange/source/SourceHandle.java