[news.eclipse.tools.emf] Re: Question about Teneo/Hibernate and Transact

[Martin Taal <mtaal@xxxxxxxxx>]

Hi Josef,
Every save results in a commit, so if you do a save on each action then you get a commit on each action, and the order 
is determined by the order of the calls to .save(..). If you do multiple actions on the model and then do one save then 
Hibernate will try to find an optimal execution order.

gr. Martin

Josef Duschl wrote:
> The objects are all in one resource. So do I read you correctly, that 
> whatever single action I perform on the model, in this case, is 
> reflected as one single commit on the database. The order of performing 
> the actions also determines the order of execution on the database.
>
> Martin Taal wrote:
>
> > Hi Josef,
> > Transactions can be handled in 2 ways:
> > - a resource has its own session and the resource.save is done in a 
> transaction managed by the resource itself
> > - resources can share a session/transaction, see here:
> http://www.elver.org/hibernate/hibernateresources.html#Sharing+one+Session+between+Resources%2C+One+transaction+when+saving+multiple+resources 
>
>
> > For the case you mention below (assuming that the objects are in 
> > different 
> resources) you have to share a session
> > between resources.
>
> > If all the objects are in one resource then the scenario you describe 
> > is not 
> possible between two save actions. In this
> > case you have to nullify the reference before deleting the referenced 
> object. So the actions can be done on the model in
> > 3 steps but can only be persisted in one save action.
>
> > This should also apply to 1.0.4 which I guess you are using.
>
> > gr. Martin
>
> > Josef Duschl wrote:
> > > Hi,
> > >
> > > How are transactions managed in the EMF/Teneo/Hibernate ressources?
> > >
> > > Ie. is it possible to do following modifications between two 
> > > ressource.save() calls?
> > >
> > > * Delete an object which is referenced by another one by foreign key 
> > > without deleting the referencing object.
> > > * Create a new object to replace the deleted one.
> > > * Make the reference point to the new object instead of the deleted one.
> > >
> > > When doing that, I get a SQL exception stating that a foreign key 
> > > constraint has been violated.
> > > Will the three modifications, when done in three separate steps on 
> > > the model, be executed as three separate operations (transactions) on 
> > > the database?
> > >
> > > Kind Regards,
> > >
> > > Josef


--

With Regards, Martin Taal

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