Re: pg_system_identifier()

Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> On 2013-08-22 08:45:38 -0700, Josh Berkus wrote:
>> However, given that the value is the same for all servers in a
>> replication set, are we sure we want to call it system_identifier? Is
>> there a better name?

> Given it's been named that and visible via pg_controldata for years I am
> against introducing confusion by renaming it.

I agree that if we have a function named pg_system_identifier(), it ought
to return the same value that pg_controldata prints under that name.
But that doesn't really answer any questions about how that value is
obtained. I think the question on the table right now is whether we like
the way that value behaves, in the context of a user-visible system ID.
In particular, do we want to think about changing things so that (1) a
slave has a different ID than the master, and/or (2) a slave's ID changes
on promotion to master. I don't know the answers to these things ---
but once we make it user visible it's going to be too late to change
its behavior, so now's the time to consider.

regards, tom lane