Details
Major Description
Since server side prefetching was not proved to be a good way to prefetch, we need to do it on client side.
This is a wrapper class that takes any instance of `ResultScanner` as the underneath scanning component. The class will schedule the scanning in a background thread. There is a buffering queue storing prefetched results, whose's length is configurable. The prefetcher will release the thread if the queue is full and wait for results to be consumed.