Re: Avoiding any locks in SQL Servers - read and understand....its magic.

"Ed Avis" <ed_at_membled.com> wrote in message news:l1wu6yj0qu.fsf_at_budvar.future-i.net...
> "VC" <boston103_at_hotmail.com> writes:
>
> >Earlier in the thread Heikki Tuuri mentioned that neither Oracle nor
> >Postgres (which mimics Oracle's concurrency mechanism) implement the
> >true SERIALIZABLE IL. Someone, I think Ed Avis, asked to give an
> >example of a scenario in which non-serializable transactions use
> >'pure' SQL without PL/SQL extensions (although I am not sure why it
> >matters).
>
> I asked because I was thinking of conformance with the ANSI SQL
> standard (or standards), and PL/SQL is not part of these standards, so
> if you want an example of where the 'serializable' isolation level is
> not properly implemented you'd need to use only plain SQL.
>
> >the following schedule (S1) whilst runnig under Oracle's SIL:
> >
> >T1(update);T2(update);T1(commit);T2(commit);
> >
> >produces a result different from the SERIAL execution (S2):
> >
> >T1(update);T1(commit);T2(update);T2(commit);
> >
> >Therefore, S1 is not serializable.
>
> Well, you need to show that it produces a result different from _any_
> serial execution, so in this case you must also check that it is

Yes, you are right about the word _any_. Thank you. I just though the other scenario was obvious ;)

>
> --
> Ed Avis <ed_at_membled.com>

Rgds.

VC Received on Sat Feb 07 2004 - 12:06:41 CST