Re: Vacuum and Transactions

On Wed, 2005-10-05 at 09:53 +0300, Hannu Krosing wrote:
> On T, 2005-10-04 at 11:10 -0400, Tom Lane wrote:
> > Rod Taylor <pg@rbt.ca> writes:
> > > The catch is that there are some other very active structures (like
> > > pg_listener for Slony) which after a couple of hours without vacuuming
> > > will quickly have the DB at an unreasonably high load (low tens) which
> > > seems to all but halt the vacuum on the large structure.
> > 
> > Yeah.  We desperately need to reimplement listen/notify :-( ... that
> > code was never designed to handle high event rates.
> 
> Sure. But it handles amazingly well event rates up to a few hundred
> events per second - given that pg_listener is cleaned up often enough.

Accomplishing the pg_listener cleanup often enough can be difficult in
some circumstances.

> It also seems that Slony can be modified to not use LISTEN/NOTIFY in
> high load situations (akin to high performance network cards, which
> switch from interrupt driven mode to polling mode if number of packets
> per second reaches certain thresolds).

I have other items in this database with high churn as well. Slony was
just an example.

--