private double missingRate() {
    if (isApproximatelyZero(pollRate())) {
      return 0.0;
    }
    return missingPrefechMeter.getOneMinuteRate() / pollRate();
  }
The {@link SubscriptionPrefetchingQueueStates} manages the state of a {@link
SubscriptionPrefetchingQueue}. It determines whether prefetching should occur based on memory
availability, poll request rates, and missing prefetch rates.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/subscription/broker/SubscriptionPrefetchingQueueStates.java