On Tue, Dec 4, 2012 at 2:05 PM, Jan Wieck <JanWieck@yahoo.com> wrote:
>> So the question on the table is which of these three intervals
>> should be GUCs, and what values to use if they aren't.
>
> I could live with all the above defaults, but would like to see more
> comments on them.
I largely agree with what's already been said. The only interval that
seems to me to maybe need its own knob is the total time after which
the autovacuum worker will give up. If we set it to 2 *
deadlock_timeout, some people might find that a reason to raise
deadlock_timeout. Since people *already* raise deadlock_timeout to
obscenely high values (a minute? an hour???) and then complain that
things blow up in their face, I think there's a decent argument to be
made that piggybacking anything else on that setting is unwise.
Against that, FWICT, this problem only affects a small number of
users: Jan is the only person I can ever remember reporting this
issue. I'm not dumb enough to think he's the only person who it
affects; but my current belief is that it's not an enormously common
problem. So the main argument I can see against adding a GUC is that
the problem is too marginal to justify a setting of its own. What I
really see as the key issue is: suppose we hardcode this to say 2
seconds. Is that going to fix the problem effectively for 99% of the
people who have this problem, or for 25% of the people who have this
problem? In the former case, we probably don't need a GUC; in the
latter case, we probably do.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company