Re: Core team statement on replication in PostgreSQL

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.

I don't think any one installation would see all of the above mentioned
scenarios, but we need to take care of multiple slaves operating off of a
single master; something similar to cascaded Slony-I.

My two cents.

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--
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