The actual database query that we use to fill the UserMessage cache
only takes a few hundred milliseconds to run; however the process of
iterating through the results would take 3-5 seconds because the
Django ORM is not very efficient for small tables where we're only
interested in the integer values in a couple columns.
So we can save most of that Tornado startup time by just doing this
one query manually; I left the original query next to it in a comment
so it is easy to keep it all up to date as we change our product.
(imported from commit ac4675bcdda5d812ebfbe211450c85ee2787ee66)
