Jan Wieck <JanWieck(at)Yahoo(dot)com> writes:
>> No, I meant how will the *function* know, if a superuser and/or some
>> background process can purge records at any time?
> The data contains timestamps which are supposedly taken in commit order.
You can *not* rely on the commit timestamps to be in exact order.
(Perhaps approximate ordering is good enough for what you want here,
but just be careful to not fall into the trap of assuming that they're
exactly ordered.)
regards, tom lane