Re: [HACKERS] Metadata about relation creation & full scans.

Andres Freund <andres@anarazel.de> writes:
> On 2017-03-22 10:14:14 -0400, Tom Lane wrote:
>> (2) How you gonna update this in vacuum?  It cannot do a transactional
>> update.

> I think we can just do that in a separate transaction, at the tail end
> of vacuum_rel() - if we crash just before that, not that much is lost.

Blech.  What if someone's queued an exclusive lock request on the table?

Actually though, maybe you could get away with updating the last-vacuum
field nontransactionally.  I think we're already updating some of the
other pg_class fields nontransactionally.
        regards, tom lane