Excerpts from Uwe Bartels's message of jue jul 01 04:42:42 -0400 2010:
> Hi Tom,
>
> till now i found more blocking vacuum processes in other databases as well.
> we migrated postgres from 8.3 to 8.4 in april.
Please examine pg_locks to see what's blocking autovacuum. The key is
WHERE granted=f.