Re: Theoretical Basis for SELECT FOR UPDATE

Tony Andrews wrote:
> vc wrote:

[...]
> > This feature is interesting because in fact it implies that the
> > hypothetical database has to implement multiversioning. How else can
> > it get the last consistent value of 'a' after 'a' has already been
> > changed ? This would exclude from consideration all purely locking
> > databases similar to DB2, SQL Server, Informix, Sybase, etc.
>
> Well I suppose the DBMS could gather all the data it will need before
> it changes any and store it temporarily somewhere?

That's what multiversioning does, more or less ;) Received on Wed Oct 05 2005 - 18:26:56 CEST