Code review comment for ~pappacena/launchpad:gitrepo-pending-merges-tuning

I think it should be possible to express an equivalent of the launchpad.View permission check on merge proposals directly in a database query. We have a good chunk of the machinery for that already (BranchCollection and GitCollection), and I think we just need to use it more effectively here.

As for the remaining limit stuff, it looks to me as though this needs to be reworked using the batch navigation system; that's normally how we handle rendering large collections.

We normally do avoid wallclock speed tests for the sorts of reasons you suggest. In most cases query count tests (especially tests for how query counts scale with the number of objects involved) are good enough proxies, and they have the great virtue of behaving deterministically. I think that would be the case here.

There's a lot of stuff to get your teeth into here! Let's discuss it at the sprint, since that's so close.