Re: ERROR: found multixact from before relminmxid

On Wed, Apr 11, 2018 at 8:31 AM, Alexandre Arruda <adaldeia(at)gmail(dot)com>
wrote:

> 2018-04-10 19:09 GMT-03:00 Peter Geoghegan <pg(at)bowt(dot)ie>:
> > On Tue, Apr 10, 2018 at 4:31 AM, Alexandre Arruda <adaldeia(at)gmail(dot)com>
> wrote:
> >> Actualy, I first notice the problem in logs by autovacuum:
> >>
> >> 2018-04-10 08:22:15.385 -03 [55477] CONTEXT: automatic vacuum of
> >> table "production.public.fn06t"
> >> 2018-04-10 08:22:16.815 -03 [55477] ERROR: found multixact 68834765
> >> from before relminmxid 73262006
> >>
> >> production=# vacuum analyze verbose fn06t;
> >> INFO: vacuuming "public.fn06t"
> >> ERROR: found multixact 76440919 from before relminmxid 122128619
> >
> > Do you think that CLUSTER was run before regular VACUUM/autovacuum
> > showed this error, though?
>
> Yes, because the table is clustered in the old database and
> reclustered when it was reloaded in the version 10.
> But the table was not clustered again.
>
>
I wonder if we're staring at some race condition in visibility map where a
previous vacuum inadvertently skips a page because the visibility map bit
is set, thus leaving behind an unfrozen multixid. The page then again
becomes !all_visible and the next vacuum then complains about the unfrozen
multixid.

Thanks,
Pavan

--
Pavan Deolasee http://www.2ndQuadrant.com/
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