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

From: Ed Avis <ed_at_membled.com>
Date: 07 Feb 2004 16:55:10 +0000
Message-ID: <l1smhmj0cx.fsf@budvar.future-i.net>


"Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> writes:

>To date, every example I have seen of Oracle failing to handle
>serialization properly has required the construction of an incorrect
>data model, so I haven't been able to get excited about the issue.

To me, this doesn't make much sense. If the database fails to handle transaction ordering correctly (according to the database-theory definition of 'serializable'), then it is not much consolation to wave hands and say this is an incorrect data model. It's a bad data model only because it's a case that the database gets wrong!

I suppose it would be okay if on executing the SQL, the programmer saw a warning:

    This transaction cannot be guaranteed to execute in a serializable     order, even though you have chosen the 'serializable' isolation     level. Please see the documentation for more details.

but it isn't like that, the database is quietly choosing to misorder the operations in two transactions, and that's something I would expect more from MySQL than an industrial-strength RDBMS like Oracle, which is good at maintaining transaction isolation in other cases.

-- 
Ed Avis <ed_at_membled.com>
Received on Sat Feb 07 2004 - 10:55:10 CST

Original text of this message

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