//分批查询：
public List<Task> batchSelectTaskList(Long id){
  List<Task> taskList = new ArrayList<>();
  int count = mapper.selectTaskCount(id);
  int limit = 500;
  int batchSelectCount = count%limit == 0 ? count/limit : count/limit+1;
  int start = 0;
  int end = 0;
  for(int i=1;i<=batchSelectCount;i++){
    //end = i==batchSelectCount ? end+count%limit : end+limit;
    end = end+limit;
    List<Task> subTaskList = mapper.batchSelect(id,start,limit);
    start = end;
    taskList.addAll(subTaskList);
  }
  return taskList;
}