Re: [Modeling-users] Rollback?

[<sbi...@us...>]

Sorry for the very late answer, for an unknown reason I did not see your =
post.

> Well, I can forbid that for the main database of my application.
> =20
>> - optimistic locking: you'll get notifications when saving changes,
>=20
> How does this work?

I was thinking of a delegate method being called by saveChanges() when it=
 notices that changes have happened in the database since the last time t=
he DB was queried (meaning that someone else has modified the db).

The delegate will receive a full view of observed modifications: the prop=
erties that have changed (attributes+relationships), objects that have be=
en deleted.  With this information any possible processing is possible: c=
ustom fusion of local+db modifications, notifying the user of a conflict =
and asking him how to solve it, ignoring changes and overriding the db ch=
anges, any combination of the previous solutions... In any case, the dele=
gate will decide whether the transaction opened by saveChanges() should b=
e cancelled for real or re-submitted after conflicts have been solved.

-- S=E9bastien.



Wolfgang Keller wrote:
>> But, given that pessimistic locking locks any data that is going to be=
=20
>> updated, if your application is transaction-intensive updating the sam=
e data,=20
>=20
>> you'll get a lot of processes waiting at the same time.
>=20
> "Waiting for Godot"
>=20
> Or, as users of SAP call it in German; "Sanduhr-Anzeige-Programm" -=20
> Hourglass-Display-Program. >:->
> =20
>> it won't even help if the framework had something like a central serve=
r on=20
>> top of the db & shared among different processes since the data still =
can=20
>> be updated directly at the database level by any other process.=20
>=20
> Well, I can forbid that for the main database of my application.
> =20
>> - optimistic locking: you'll get notifications when saving changes,
>=20
> How does this work?
>=20
>> giving you the opportunity to examine the change and, e.g., automatica=
lly=20
>> handle them or provide feedback to the user.=20
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> That would be what I am looking for.
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> Sincerely,
>=20
> Wolfgang Keller
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