public synchronized void setNoMoreTsBlocks(int lastSequenceId) {
    if (LOGGER.isDebugEnabled()) {
      LOGGER.debug("[ReceiveNoMoreTsBlockEvent]");
    }
    this.lastSequenceId = lastSequenceId;
    if (!blocked.isDone() && remoteTsBlockedConsumedUp()) {
      blocked.set(null);
    }
    if (isFinished()) {
      sourceHandleListener.onFinished(this);
    }
  }
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