Re: Synchronization levels in SR

On Tue, May 25, 2010 at 1:18 AM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> I see a lot of value in #4; it makes it possible to distribute read-only
> load to the standby using something like pgbouncer, completely transparently
> to the application.

Agreed.

> In the lesser modes, the application can see slightly
> stale results.

Yes

BTW, even if we got #4, we would need to be careful about that
we might see the uncommitted results from the standby. That is,
the transaction commit might become visible in the standby before
the master returns its "success" to a client. I think that we
would never get the completely-transaction-consistent results
from the standby until we have implemented the "snapshot cloning"
feature.
http://wiki.postgresql.org/wiki/ClusterFeatures#Export_snapshots_to_other_sessions

> But whatever we can easily implement, really. Pick one that you think is the
> easiest and start with that, but keep the other modes in mind in the design
> and in the user interface so that you don't paint yourself in the corner.

Yep, the design and implementation for #2 and #3 should be
easily extensible for #4. I'll keep in mind that.

Regards,

--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center