Re: slow vacuum performance

Hi Bill,
I am vacuuming every 24 h.
I have a cron script about i.
But if I make massive update (for example it affects 1 M rows) and I start vacuum,
it take this 2 h.
Also I will note, that this massive update is running in one transaction ( I can
not update 100K and start vacuum after it).

regards,
ivan.

Bill Moran wrote:

> pginfo wrote:
> > Hi,
> >
> > I am running pg 7.4.1 on linux box.
> > I have a midle size DB with many updates and after it I try to run
> > vacuum full analyze.
> > It takes about 2 h.
> > If I try to dump and reload the DB it take 20 min.
> >
> > How can I improve the vacuum full analyze time?
>
> How often are you vacuuming? If you've gone a LONG time since the last vacuum,
> it can take quite a while, to the point where a dump/restore is faster.
>
> A recent realization that I've had some misconceptions about vacuuming led me
> to re-read section 8.2 of the admin guide (on vacuuming) ... I highly suggest
> a review of these 3 pages of the admin manual, as it contains an excellent
> description of why databases need vacuumed, that one can use to determine how
> often vacuuming is necessary.
>
> --
> Bill Moran
> Potential Technologies
> http://www.potentialtech.com