Re: [holger: Re: Logger for libgda]

[David Marín Carreño <davefx bigfoot com>]

On 28 Nov 2000, Rodrigo Moya wrote:

> 
> so, you're going to save the changes? But this is not reliable at all.
> Imagine I use:
> 
> UPDATE employees SET name = 'fulano';
> 
> ok, what you save here? that employees.name was set to 'fulano'? This is
> ok, you've got a log of
> what you've done in the DB. But, how will you recover the old data?

Seeking the last value of name before 'fulano'.

> 
> This would be easy if you always used expressions such as:
> 
> UPDATE employees SET salary = salary + 200;
> 
> here, it's easy, you can recover by just doing
> 
> UPDATE employees SET salary = salary - 200;
> 
> But with other kind of expressions, I don't see the way you're going
> to recover the old data when undoing.

Each time we change the database, we log it. Since the creation of the
entry, until the last modifications. All are logged. So if we want to
undo, we look for the last modification before the modification we want to
undo.

> 
> > > > 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 ;-)
> > 
> the undoing stuff is the problem. I'd implement just a logger in 3/4 hours,
> 
> but the undoing stuff... I can't see the way we'll implement it.

I hope this message give you a clue.

> 
> cheers
> 
> 
> 

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