Обсуждение: Best Practice for running vacuums during off hours WAS Re: Autovacuum launcher doesn't notice death of postmaster immediately

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 6/7/07, Matthew T. O'Connor  wrote:
> Tom Lane wrote:
> > "Andrew Hammond"  writes:
> >> Hmmm... it seems to me that points new users towards not using
> >> autovacuum, which doesn't seem like the best idea. I think it'd be
> >> better to say that setting the naptime really high is a Bad Idea.
> >
> > It seems like we should have an upper limit on the GUC variable that's
> > less than INT_MAX ;-).  Would an hour be sane?  10 minutes?
> >
> > This is independent of the problem at hand, though, which is that we
> > probably want the launcher to notice postmaster death in less time
> > than autovacuum_naptime, for reasonable values of same.
>
> Do we need a configurable autovacuum naptime at all?  I know I put it in
> the original contrib autovacuum because I had no idea what knobs might
> be needed.  I can't see a good reason to ever have a naptime longer than
> the default 60 seconds, but I suppose one might want a smaller naptime
> for a very active system?

That's a good question. I can't see any reason for a naptime longer
than 60 seconds either.

I think very large naptime settings are a symptom of another issue:
what's the Right Way to defer vacuums until "off hours"? Is that even
a desirable thing anymore? I don't think it is in the majority of
cases.

I originally thought that this was more of a Best Practices issue (ie,
fix in the docs, not the code), but now I'm wondering if there's much
call for supporting the idea of being more aggressive with vacuums at
different times of the day / week / month. Anyone?
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.7 (Darwin)

iD8DBQFGaIdN+zlEYLc6JJgRAiNFAJ49CQwiTVxWhXNeOzIBABLN5LZY3wCfUj/W
ZLakjPyRVwOijaB6keS3ld8=
=Hg/X
-----END PGP SIGNATURE-----

Andrew Hammond escribió:

> That's a good question. I can't see any reason for a naptime longer
> than 60 seconds either.
> 
> I think very large naptime settings are a symptom of another issue:
> what's the Right Way to defer vacuums until "off hours"? Is that even
> a desirable thing anymore? I don't think it is in the majority of
> cases.
> 
> I originally thought that this was more of a Best Practices issue (ie,
> fix in the docs, not the code), but now I'm wondering if there's much
> call for supporting the idea of being more aggressive with vacuums at
> different times of the day / week / month. Anyone?

That's why the intention is to have the autovacuum scheduling feature
be a mechanism for changing the autovac parameters according to date and
time.  We even have a Google Summer of Code project about that.

-- 
Alvaro Herrera                 http://www.amazon.com/gp/registry/DXLWNGRJD34J
"La virtud es el justo medio entre dos defectos" (Aristóteles)