protected boolean isEmpty(int index) {
    return inputTsBlocks[index] == null || inputTsBlocks[index].isEmpty();
  }
If the tsBlock is null or has no more data in the tsBlock, return true; else return false.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/operator/process/AbstractConsumeAllOperator.java