Re: UNDO and in-place update

2016-11-25 1:44 GMT+01:00 Robert Haas <robertmhaas(at)gmail(dot)com>:

> On Thu, Nov 24, 2016 at 6:20 PM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
> wrote:
> >> I think that the whole emphasis on whether and to what degree this is
> >> like Oracle is somewhat misplaced. I would look at it a different
> >> way. We've talked many times over the years about how PostgreSQL is
> >> optimized for aborts. Everybody that I've heard comment on that issue
> >> thinks that is a bad thing.
> >
> >
> > again this depends on usage - when you have a possibility to run VACUUM,
> > then this strategy is better.
> >
> > The fast aborts is one pretty good feature for stable usage.
> >
> > Isn't possible to use UNDO log (or something similar) for VACUUM?
> ROLLBACK
> > should be fast, but
> > VACUUM can do more work?
>
> I think that in this design we wouldn't use VACUUM at all. However,
> if what you are saying is that we should try to make aborts
> near-instantaneous by pushing UNDO actions into the background, I
> agree entirely. InnoDB already does that, IIUC.
>

ok, it can be another process - that can be more aggressive and less
limited than vacuum.

Regards

Pavel

>
> --
> Robert Haas
> EnterpriseDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
>