Re: Add database to PGXACT / per database vacuuming

On Fri, Aug 30, 2013 at 2:29 PM, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
>> I don't know how big an impact adding the database oid would have, on the
>> case that the PGPROC/PGXACT split was done in the first place. In the worst
>> case it will make taking a snapshot 1/3 slower under contention. That needs
>> to be tested.
>
> Yes, definitely. I am basically wondering whether somebody has/sees
> fundamental probles with it making it pointless to investigate.

I expect there will be a measurable performance degradation, though
I'm willing to be proven wrong. I think the question is whether we
get enough bang for the buck out of it to eat that. It seems quite
likely that users with many databases will come out ahead, as such
systems seem likely to be shared hosting environments where the
machine is lightly loaded most of the time anyway, but where
cross-database interactions cause headaches. But many users have One
Big Database, and AFAICS this is just overhead for them.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company