Обсуждение: Can autovac try to lock multiple tables at once?

$subject would be bad because of potential deadlocks against other
transactions that might try to exclusive-lock more than one table.

We should be OK for actual vacuum operations, but I think that if
autovac chooses to just ANALYZE multiple tables, it will do it in
one transaction and accumulate locks.  Probably the use_own_xacts
logic in vacuum() ought to special-case IsAutoVacuumWorkerProcess.
        regards, tom lane

Tom Lane wrote:
> $subject would be bad because of potential deadlocks against other
> transactions that might try to exclusive-lock more than one table.
>
> We should be OK for actual vacuum operations, but I think that if
> autovac chooses to just ANALYZE multiple tables, it will do it in
> one transaction and accumulate locks.  Probably the use_own_xacts
> logic in vacuum() ought to special-case IsAutoVacuumWorkerProcess.

Sure, it can do that.  I think it's easy enough to correct this problem;
see attached patch.  Should this be backpatched?  Earlier releases also
fall foul of this problem AFAICT.

--
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

Alvaro Herrera <alvherre@commandprompt.com> writes:
> Sure, it can do that.  I think it's easy enough to correct this problem;
> see attached patch.  Should this be backpatched?  Earlier releases also
> fall foul of this problem AFAICT.

Yeah, because what made me think about it was a gripe from an 8.2
user ... maybe this wasn't his problem, but it could be.
        regards, tom lane

Tom Lane wrote:
> Alvaro Herrera <alvherre@commandprompt.com> writes:
> > Sure, it can do that.  I think it's easy enough to correct this problem;
> > see attached patch.  Should this be backpatched?  Earlier releases also
> > fall foul of this problem AFAICT.
> 
> Yeah, because what made me think about it was a gripe from an 8.2
> user ... maybe this wasn't his problem, but it could be.

Backpatched all the way back to 8.1.

-- 
Alvaro Herrera                          Developer, http://www.PostgreSQL.org/
Y dijo Dios: "Que sea Satanás, para que la gente no me culpe de todo a mí."
"Y que hayan abogados, para que la gente no culpe de todo a Satanás"