Re: pg_system_identifier()

On 2013-08-22 12:18:41 -0400, Bruce Momjian wrote:
> On Thu, Aug 22, 2013 at 06:18:39PM +0200, Andres Freund wrote:
> > But essentially we already have something like that by the combination
> > of system identifier and timeline id. Admittedly there's the weakness
> > that the timelineid can increase the same on several machines in the
> > cluster but that's a weakness we ought to fix sometime independent of
> > this.
> >
> > So maybe the answer is to also expose the current timeline?
> >
> > An alternative would be to have a pg_controldata_values() SRF...
>
> It seems the value is more of a _cluster_ identifier than a system
> identifier. We don't allow cross-major-version replication, so I am
> confused why we can't rename it in 9.4.

For one, it would introduce confusion for the not inconsiderable number
of people already knowing the variable. For another, it's exposed via
the replication protocol's IDENTIFY SYSTEM.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
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