Re: Re: [COMMITTERS] pgsql: Ensure age() returns a stable value rather than the latest value

On lör, 2012-05-12 at 12:59 -0400, Tom Lane wrote:
> Now it's entirely likely that there is nobody out there relying on
> such a thing, but nonetheless this is a compatibility break, and an
> unnecessary one IMO. You haven't shown any convincing reason why we
> need to change the behavior of age() on master servers at all.

Recall that this thread originally arose out of age() being called by a
monitoring tool. It would be nice if repeatedly calling age() on an
otherwise idle database would not change the result. Currently, you
would never get a "stable" state on such a check, and moreover, you
would not only get different results but different long-term behavior
between master and standby. Now this is not that important and can be
accommodated in the respective tools, but it is kind of weird. It would
be like a check for disk space losing one byte at every check, even if
you got it back later.