- you want to be able to read uncommitted data
My original reponse was probably to specific to the initial problem. I think
the issues with the different transaction isolation are quite large and
application specific so I will not go into here. But it does beg the
question when is the right time to save changes after every field, after 2
fields changes after all changes (how can we determine this), etc.... Also
how can we correctly instruct the container what way we would like it to
do(assuming cmp)? Bear in mind we do not have nested transaction support we
could solve some problems.
- the update order is not respected with commit-at-end-of-tx, and you have
constraints set in your DB (example : suppose you create a book and an
author in
I do not think this falls into the same problem as I discussed since the
ejbCreate has different semantics than normal entity bean access. We can
assume the jdbc call for this will be done immediately since the primary key
needs validation. What I was refering to was normal write method calls on a
cmp entity bean.
William
> -----Original Message-----
> From: Jean-Baptiste Nizet [SMTP:[EMAIL PROTECTED]]
> Sent: Tuesday, February 22, 2000 11:20 AM
> To: [EMAIL PROTECTED]
> Subject: Re: trying to come up with a design pattern to solve
> acommonJ2EEproblem
>
> "Louth, William (Exchange)" wrote:
>
> > Would they really write to the database more often, this seems like a
> real
> > performance overhead. Its bad enough that some containers do not even
> > support tuned writes never mind this. I really cannot imagine a reason
> for
> > this especially since the bean could be updated many times during a
> > transaction with each changes ending up with a sql call.
> >
>
> I can imagine some reasons :
> - you want to be able to read uncommitted data
> - the update order is not respected with commit-at-end-of-tx, and you have
> constraints set in your DB (example : suppose you create a book and an
> author in
> the same tx, and that the book contains a foreign key pointing to the new
> author. If there is a constraint in your DB that the author key must
> exist, and
> if the book is inserted first, you will have an error. Instead, if the
> author is
> inserted first, no problem.)
>
> JB.
>
> >
> > William
> >
> > > -----Original Message-----
> > > From: Stu Halloway [SMTP:[EMAIL PROTECTED]]
> > > Sent: Monday, February 21, 2000 8:07 PM
> > > To: [EMAIL PROTECTED]
> > > Subject: Re: trying to come up with a design pattern to solve
> > > acommonJ2EE problem
> > >
> > > > It won't be in the database because the transaction has not yet
> > > > completed, thus the EJB server has not yet committed the changes.
> (EJB
> > > > users write-at-commit)
> > >
> > > Maybe, maybe not. EJB server can write to the database more often
> than
> > > that. Vendor's option.
> > >
> > > > Changes made to the database are visible immediately in the same
> > > > transaction.
> > >
> > > I believe that this is database-vendor-specific, and might not always
> be
> > > true. (Although it is the behavior I have always seen.)
> > >
> > > Stuart Halloway
> > > DevelopMentor
> > > http://www.develop.com/hp/halloway
> > >
> > >
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> --
> Jean-Baptiste Nizet
> [EMAIL PROTECTED]
>
> R&D Engineer, S1 Belgium
> Excelsiorlaan 87
> B-1930 Zaventem
> +32 2 714 45 42
>
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