Fork of #15384

The time from starting the search to finding a match is very short, but then we sit on that match for 100+ seconds, because we don't send results to the frontend until we've filled a batch of 512. Since there are fewer than a full batch of results, nothing is visible until the search is over. So we could increase the perceived performance quite a lot by adding a timeout to send intermediate results over if the batch doesn't fill up.