Re: solving wraparound

On Sat, Dec 31, 2005 at 10:34:51AM -0500, Matthew T. O'Connor wrote:
> Anyone think it might be reasonable to add a GUC option that tells
> autovacuum to monitor for wraparound only, and not for more general
> usage based vacuuming? Something like autovac_wraparound_only. Not
> sure I like the idea, but thought it might be worth some discussion.

We don't want the autovacuum to be running the whole time monitoring
for something that won't happen to most people. But I think something
like:

spawn_autovacuum_on_wraparound_danger=true

Ie, when you reach the billion transaction mark and postmaster begins
emitting warning, it will, once off, spawn autovacuum to vacuum the
most neediest database.

ISTM that many people who run into wraparound issue don't because they
don't have a vacuum policy, but because they made one very clever but
forgot to do the catalog or something else. Having the postmaster
spawning it once every billion transactions seems sensible enough.

Only question, does it rely on other options (like stats) to work for
this purpose?
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a
> tool for doing 5% of the work and then sitting around waiting for someone
> else to do the other 95% so you can sue them.