Re: age(xid) on hot standby

Alvaro Herrera <alvherre@commandprompt.com> writes:
> Excerpts from Peter Eisentraut's message of dom ene 15 10:00:03 -0300 2012:
>> On ons, 2011-12-28 at 14:35 -0500, Tom Lane wrote:
>>> The trouble with using ReadNewTransactionId is that it makes the results
>>> volatile, not stable as the function is declared to be.

>> Could we alleviate that problem with some caching within the function?

> Maybe if we have it be invalidated at transaction end, that could work.
> So each new transaction would get a fresh value.

Yeah, I think that would work.

> If you had a long
> running transaction the cached value would get behind, but maybe this is
> not a problem or we could design some protection against it.

Nobody has complained about the fact that age()'s reference point
remains fixed throughout a transaction on the master, so I don't see why
we'd not be happy with that behavior on a standby.
        regards, tom lane