> Stephan Szabo <sszabo@megazone.bigpanda.com> writes:
>> Right, but since the how to resolve it currently involves executing a
>> query, simply stopping dead won't allow you to resolve it. Also, if we
>> stop at the exact wraparound point, can we run into problems actually
>> trying to do the vacuum if that's still the resolution technique?
>
> We'd have to do something with a fair amount of slop. The idea I was
> toying with just now involved a forcible shutdown once we get within
> say 100,000 transactions of a wrap failure; but apply this check only
> when in interactive operation. This would allow the DBA to perform
> the needed VACUUMing manually in a standalone backend.
>
> The real question here is exactly how large a cluestick do you want to
> hit the DBA with. I don't think we can "guarantee" no data loss with
> anything less than forced shutdown, but that's not so much a cluestick
> as a clue howitzer.
I think a DBA or accidental DBA would prefer stating in a meeting:
"Yea, the database shut down because I didn't perform normal maintenence,
its fixed now and we have a script in place so it won't happen again"
Over
"Yea, the database lost all its data and we have to restore from our last
backup because I didn't perform normal maintenence."
One gets a "boy are you lucky" over a "you're fired."
>
> Maybe
>
> (a) within 200,000 transactions of wrap, every transaction start
> delivers a WARNING message;
>
> (b) within 100,000 transactions, forced shutdown as above.
I agree.