Re: Core team statement on replication in PostgreSQL

On Fri, 2008-05-30 at 12:31 +0530, Gurjeet Singh wrote:
> On Fri, May 30, 2008 at 10:40 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> But since you mention it: one of the plausible answers for
> fixing the
> vacuum problem for read-only slaves is to have the slaves push
> an xmin
> back upstream to the master to prevent premature vacuuming.
> The current
> design of pg_standby is utterly incapable of handling that
> requirement.
> So there might be an implementation dependency there,
> depending on how
> we want to solve that problem.
>
> I think it would be best to not make the slave interfere with the
> master's operations; that's only going to increase the operational
> complexity of such a solution.
>
> There could be multiple slaves following a master, some serving
> data-warehousing queries, some for load-balancing reads, some others
> just for disaster recovery, and then some just to mitigate human
> errors by re-applying the logs with a delay.

Agreed.

We ruled that out as the-only-solution a while back. It does have the
beauty of simplicity, so it may exist as an option or possibly the only
way, for 8.4.

--
Simon Riggs www.2ndQuadrant.com
PostgreSQL Training, Services and Support