For all I can see everything we do ought to be parallel safe by postgres standards (i.e., we don't touch anything within the database at all).

Classic use cases (such as our healpix maps) profit greatly from parallel plans -- so, what about a round of declaring our functions PARALLEL SAFE?

The one problem I see at this point: How do we upgrade existing installations without going insane? Enumerating all the signatures in an endless ALTER FUNCTION sequence looksreally unattractive to me...