Re: Good name for new lock type for VACUUM?

> "Hiroshi Inoue" <Inoue(at)tpf(dot)co(dot)jp> writes:
> > Isn't it a better idea to have a separate 'SELF EXCLUSIVE' lock
> > which conflicts with only itself ?
> >>
> >> *Only* itself? What would that be useful for?
>
> > Isn't VacuumLock = RowExclusiveLock + SelfExclusiveLock
> > for the table ?
>
> Oh, I see, you're suggesting acquiring two separate locks on the table.
> Hmm. There would be a risk of deadlock if two processes tried to
> acquire these locks in different orders. That's not a big problem for
> VACUUM, since all processes would presumably be executing the same
> VACUUM code. But it raises questions about just how useful this lock
> type would be in general-purpose use. You could never acquire *only*
> this lock type, it'd have to be combined with something else, so it
> seems like any usage would have to be carefully examined for deadlocks.
>
> Still, it's an interesting alternative. Comments anyone?

SelfExclusiveLock is clear and can't be confused with other lock types.

--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026