@Override
  protected DriverTask remove(DriverTask driverTask) {
    checkArgument(driverTask != null, "driverTask is null");
    if (highestPriorityLevelQueue.remove(driverTask)) {
      return driverTask;
    }
    for (PriorityQueue<DriverTask> level : levelWaitingSplits) {
      if (level.remove(driverTask)) {
        return driverTask;
      }
    }
    return null;
  }
During periods of time when a level has no waiting splits, it will not accumulate scheduled
time and will fall behind relative to other levels.

<p>This can cause temporary starvation for other levels when splits do reach the
previously-empty level.

<p>To prevent this we set the scheduled time for levels which were empty to the expected
scheduled time.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/schedule/queue/multilevelqueue/MultilevelPriorityQueue.java