Re: [holger: Re: Logger for libgda]

[David Marín Carreño <davefx bigfoot com>]

On 28 Nov 2000, Rodrigo Moya wrote:

> > Anyway, you have to fetch the data a transaction attempts to modify 
> > from the server before applying that transaction, and log that data first.
> > This would be a great hint for avoiding collision of multiple transactions
> > from multiple systems:
> >  Client a modifies some data and commits transaction. After that, client b
> >  modifies the commited data (making it right again and applying some updates)
> >  and commits his transaction. Now client a issues an undo. Updates of client
> >  b would be lost, because they're not in the log of client a.
> > 
> 
> yes, another problem that is raised now. Special care should be taken to
> avoid this. And I ask
> again: how could we do that?

After any change in the database, the log mustn't save the old status. It
must save the changes. It is slower when undoing, but it hasn't this
problem.

And the log must be written only when the transaction has already 
finished.

> > Hope this problems can be solved, because i think having multiple
> > undo levels on transactions is a great idea and a valuable feature
> > for libgda!
>
> I also like the idea of having the logger in GDA, but only if we find
> a good way of handling all these problems (and others that will
> appear). But remember that if it's going to be in GDA, it should be as
> generic as possible, making it suitable for ANY data source supported
> by GDA.

I cannot see any problem here... Sorry ;-)

Greetings

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