Robert Haas <robertmhaas@gmail.com> writes:
> On Wed, Jul 19, 2017 at 1:35 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Alternatively, we could turn the origin point for abstime into
>> pg_control field, and regard changing it as a reason for a database
>> not being pg_upgrade'able unless it lacks any abstime columns.
> I would be OK with that, too, but is there any danger that we're going
> to grow pg_control to a size where reads and writes can no longer be
> assumed atomic, if we keep adding things?
Hm. Currently sizeof(struct ControlFileData) = 296, at least on my
machine. Letting it grow past 512 would be problematic. It's hard
to see getting to that any time soon, though; we don't add fields
there often.
Note that I'm not seriously pushing for this solution. I'm just trying
to make sure that we've considered all the reasonable options.
regards, tom lane