private boolean tryToGetNextTsBlock() throws Exception {
    if (canCallNext) { // if we can call child.next(), we call that and cache it in
      // cachedTsBlock
      canCallNext = false;
      TsBlock nextTsBlock = child.nextWithTimer();
      // child operator's calculation is not finished, so we just return null
      if (nextTsBlock == null || nextTsBlock.isEmpty()) {
        return false;
      } else { // otherwise, we cache it
        updateCachedData(nextTsBlock);
        return true;
      }
    }
    return false;
  }
Try to get next TsBlock

@return true if we succeed to get next TsBlock and add it into cachedTsBlock, otherwise false
@throws Exception errors happened while getting next batch data
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/operator/process/AbstractLinearFillOperator.java