Re: Changing isolation level?

SELECT... FOR UPDATE {WAIT | NOWAIT} springs to mind...

        David

(rm ns beside @ in return email address)

On Thu, 4 Dec 2003 05:59:46 +1100, "Howard J. Rogers" <hjr_at_dizwell.com> wrote:

>
>Time to don the Devil's Advocate costume, I think.
>
>I can think of lots of cases where it would be rather unfortuate to see an
>old piece of data just prior to it being changed. Rather than see the old
>data, I could well imagine that it would be more helpful to see nothing
>until the situation stabilises.
>
>If I have a customer demanding to know whether I have a turbo-widget in
>stock, I can select from my products table to check. It tells me I have one
>such item left. Mrs. Miggens therefore, on the strength of that, undertakes
>the arduous two-hour journey from remote rural New South Wales into the City
>Centre to pick up said turbo-widget. Unbeknownst to her, however, the
>information I gave her was wrong, because at the time I did my query, Fred
>in the next cubicle was selling the same product to Miss Marple. He hadn't
>committed the transaction, which is why I saw a stock level of 1. But it
>would have been nice not to give the wrong info out to Mrs. Miggens. I
>suppose I could have badgered her into placing an order, because then my
>attempt to update the stock level myself would have failed. But Mrs. Miggens
>ran into a bit of credit rating trouble a while back, and doesn't have a
>credit card. The most she can do on the phone is to enquire.
>
>There are two choices there, I suppose: see nothing at all (the blocking
>idea). Or see a stock level of 0 (the dirty reads issue beloved of, er,
>certain other products). Oracle's long-time answer has been: you'll see 1,
>and only 1, and nothing else, ever... which some might consider to be a lack
>of choice in answering technology.
>
>Regards
>HJR
>
>
>
>
Received on Wed Dec 03 2003 - 14:38:35 CST