Re: do only critical work during single-user vacuum?

On Thu, Feb 3, 2022 at 4:58 PM Andres Freund <andres@anarazel.de> wrote:
>
> Hi,
>
> On 2022-02-03 16:18:27 -0500, John Naylor wrote:
> > I just checked some client case notes where they tried just that
> > before getting outside help, and both SELECT and VACUUM FREEZE
> > commands were rejected.
>
> What kind of SELECT was that? Any chance it caused a write via functions, a
> view, whatnot? And what version? What was the exact error message?

Looking closer, there is a function defined by an extension. I'd have
to dig further to see if writes happen. The error is exactly what
we've been talking about:

2022-01-03 22:03:23 PST ERROR: database is not accepting commands to
avoid wraparound data loss in database "<redacted>"
2022-01-03 22:03:23 PST HINT: Stop the postmaster and vacuum that
database in single-user mode. You might also need to commit or roll
back old prepared transactions.

-- 
John Naylor
EDB: http://www.enterprisedb.com