Re: visibility map corruption

On Fri, Jul 23, 2021 at 05:47:18PM -0700, Peter Geoghegan wrote:
> > I could perhaps see corruption happening if pg_control's oldest xid
> > value was closer to the current xid value than it should be, but I can't
> > see how having it 2-billion away could cause harm, unless perhaps
> > pg_upgrade itself used enough xids to cause the counter to wrap more
> > than 2^31 away from the oldest xid recorded in pg_control.
> >
> > What I am basically asking is how to document this and what it fixes.
> 
> ISTM that this is a little like commits 78db307bb2 and a61daa14. Maybe
> take a look at those?

Agreed.  I just wanted to make sure I wasn't missing an important aspect
of this patch.  Thanks.

-- 
  Bruce Momjian          https://momjian.us
  EDB                                      https://enterprisedb.com

  If only the physical world exists, free will is an illusion.