@Override
  protected DriverTask get(DriverTask driverTask) {
    // We do not support get() for MultilevelPriorityQueue since it is inefficient and not
    // necessary.
    throw new UnsupportedOperationException(
        "MultilevelPriorityQueue does not support access element by get.");
  }
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