Re: Manual anti-wraparound vacuums

Excerpts from Robert Haas's message of vie nov 11 12:29:42 -0300 2011:
> On Fri, Nov 11, 2011 at 9:59 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > In another thread, Alvaro quoted from the manual:
> >>       If for some reason autovacuum fails to clear old XIDs from a table, the
> >>       system will begin to emit warning messages like this when the database's oldest
> >>       XIDs reach ten million transactions from the wraparound point:
> >
> >>       WARNING:  database "mydb" must be vacuumed within 177009986 transactions
> >>       HINT:  To avoid a database shutdown, execute a database-wide VACUUM in "mydb".
> >
> >>       (A manual VACUUM should fix the problem, as suggested by the hint; but
> >>       note that the VACUUM must be performed by a superuser, else it will fail to
> >>       process system catalogs and thus not be able to advance the database's
> >>       datfrozenxid.)
> >
> > It occurs to me to wonder how this scenario will interact with the
> > recent changes to let VACUUM skip pages.  AFAIR there is not a way for a
> > manual VACUUM to set the anti-wraparound mode, is there?
>
> I tweaked Simon's original patch to address exactly this scenario;
> VACUUM FREEZE prevents page-skipping behavior.

Hmm, so should the manual suggest using VACUUM FREEZE?

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Álvaro Herrera <alvherre(at)commandprompt(dot)com>
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