Re: Freezing without cleanup lock

Jim Nasby wrote:
> While warning a client that just did a Slony-based version upgrade to make
> sure to freeze the new database, it occurred to me that it should be safe to
> freeze without the cleanup lock. This is interesting because it would allow
> a scan_all vacuum to do it's job without blocking on the cleanup lock.
> 
> Does anyone have a feel for whether scan_all vacuums blocking on the cleanup
> lock is an actual problem?

Yeah, I remember we discussed this and some other possible improvements
related to freezing.  I think other ideas proposed were that (1) during
an emergency (uncancellable) autovacuum run, we process only the tables
that are past the age limit, and (2) we remove the cost-based sleep so
that it finishes as quickly as possible.  (Yours is (3) only freeze and
not do any actual pruning -- did I get that right?)

-- 
Álvaro Herrera                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services