Re: autovacuum_freeze_max_age

Hi Tom,

At 02:51 10/11/2007, Tom Lane wrote:
>Uh, no, it's called only when we've advanced datfrozenxid,
>which is a pretty uncommon event. So I think the real hole in the
>proposal is that there would be a long and not-very-predictable delay
>between changing the parameter and having it really take effect.

Well, I believe in a situation where you need to change its value, it
would happen quite "soon".

>If there were a big use-case for changing this setting on the fly then
>I'd be more worried about it, but I don't see one really ...

Just found out that the default value had one less "0" than I thought
and that it was the reason autovacuum was vacuuming 20 GB+
insert-only tables every 3 days or so on a box of ours... And that it
needs an outage (or a switchover to the slave, actually) to change
the value, when it does not seem obvious why.

It's really just a matter of being able to change any setting that
can be at runtime rather than having to restart. A few of them can be
pretty annoying (e.g. max_connections and such), but are
understandable given what's required to make it possible to change
them, but if there's no real reason... :-)

Jacques.