I wrote:
> So maybe we should revisit the question. It'd be worth collecting some
> stats about how much extra space would be needed if we force there
> to be room for a sentinel.
Actually, after ingesting more caffeine, the problem with this for aset.c
is that the only way to add space for a sentinel that didn't fit already
is to double the space allocation. That's a little daunting, especially
remembering how many places deliberately allocate power-of-2-sized
arrays.
You could imagine deciding that the space classifications are not
power-of-2 but power-of-2-plus-one, or something like that. But that
would be very invasive to the logic, and I doubt it's a good idea.
regards, tom lane