Re: emergency outage requiring database restart

Merlin Moncure <mmoncure@gmail.com> writes:
> What if the subsequent dataloss was in fact a symptom of the first
> outage?  Is in theory possible for data to appear visible but then be
> eaten up as the transactions making the data visible get voided out by
> some other mechanic?  I had to pull a quick restart the first time and
> everything looked ok -- or so I thought.   What I think was actually
> happening is that data started to slip into the void.   It's like
> randomly sys catalogs were dropping off. I bet other data was, too.  I
> can pull older backups and verify that.  It's as if some creeping xmin
> was snuffing everything out.

Might be interesting to look at age(xmin) in a few different system
catalogs.  I think you can ignore entries with age = 2147483647;
those should be frozen rows.  But if you see entries with very large
ages that are not that, it'd be suspicious.
        regards, tom lane