Re: Autovacuum on by default?

On Tue, Aug 29, 2006 at 09:23:53PM -0700, Josh Berkus wrote:
> Peter,
> 
> > OK, it seems that while everyone wants autovacuum be more aggressive by
> > default, no one has any good data to support one setting or another.  I
> > so I suggest that we just cut scale factor and base threshold in half
> > right now (so it'd be 0.2, 0.1, 500, 250) and see about a
> > better-researched setting for the next release.
> 
> I'd recommend actually 0.4 and 0.2 and 200 and 100.  I think that 20% and 10% 
> are too aggresive.  0.4 and 0.2 are what I've been using in production on 
> many machines.  On the other hand, I think that the thresholds are much too 
> high -- that means that many small tables may never get vacuumed at all, even 
> after 100% row replacement.
Do you think .2 and .1 (or even .08 and .04, as suggested by the default
page fill percentage) are too aggressive *on small systems*? IMO, these
defaults are meant more for less experienced folks, which are much more
likely to be running a smaller database than a large one.

FWIW, I've been using .2 and .1 (as well as cutting the thresholds
down; typically to between 200 and 400 and 100 and 200) without issue,
though I did tweak the delay costs at one customer.

> I'll admit, however, that I don't have test data to support this.  
> Unfortunately we never got to good Autovac tests on the STP before it went 
> down.
-- 
Jim C. Nasby, Sr. Engineering Consultant      jnasby@pervasive.com
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461