Yep, I think all of us would agree that
to use DB constraints (1) in pair with EJB-imposed (business) constraints
(2)
in development stage helps, because :
(1) highlights inconsistencies in (2).
Once semantics of (2) are fine-tuned, (1) can be dropped.
Viktor Gritsenko
----- Original Message -----
From: Eddie Fung <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Sunday, July 23, 2000 8:09 PM
Subject: Re: Use DB constraints with EJB's or not?
> The question of DB constraints on EJB maintained code is not just an EJB
> thing but rather something that has to be considered in the build of an
> application (EJB, CORBA, whatever..).
>
> The obvious pro is that the 'belt and braces' approach gives an extra
> level of safety which has come in handy as Robert has pointed out.
>
> The con is, of course, the DBMS overheads and the overhead in maintaining
> the constraints. Specifically:
> - any insert/update/delete activity may have the overhead of the DBMS
> constraint checking (foreign key constraint) depending on whether the row
> has RI. The more foreign keys that are changed, the higher the overhead
> - in testing and production maintenance, the need to load the tables in
the
> right order, or disable and re-enable the constraints in the right order
if
> any data is bulk loaded completely
> Personally, having unique constraints is fine but having RI constraints
can
> reduce the performance of OLTP systems. To a certain degree the fact that
> we are modularising the code to maintain objects (and hence rows in the
> database) helps us to localise errors. I think that one could use
> constraints in the development phase (to check for logic errors) and even
> in production (if the transaction rate is not that high). However if
> performance drags as a result of the RI , it's the first thing I'd dump..
>
> cheers,
>
> Eddie
>
>
>
>
> At 03:40 23/07/00 -0400, you wrote:
> >Robert says:
> ><<
> >Not using a proven mechanism such as database
> >constraints to enforce constraints in your model to me would be like not
> >wearing your seatbelt because you are afraid of wrinkles in your suite.
> > >>
> >
> >I would say that:
> >
> >Not using an extraneous mechanism
> >such as database inegrity constraints
> >in addition to EJB
> >to enforce the same thing (relational integrity) second time
> >to me would be like
> >not wearing two pairs of underwear
> >(I think one pair is sufficient).
> >
> >Plus, the belief that more of the same thing is better calls for having
the
> >same thing more than twice.
> >
> >If that's the concept, should one wrap the wrapper, and then wrap it
again,
> >and again...
> >
> >I think excess as concept is unnatural.
> >
> >
> >Viktor Gritsenko
> >
> >----- Original Message -----
> >From: Robert Krueger <[EMAIL PROTECTED]>
> >To: <[EMAIL PROTECTED]>
> >Sent: Sunday, July 23, 2000 1:22 PM
> >Subject: Re: Use DB constraints with EJB's or not?
> >
> >
> > > At 17:11 23.07.00 , you wrote:
> > > >Hi,
> > > >
> > > >I had a discussion with a colleque of mine and we did not reach a
> >agreement,
> > > >maybe some experts on this mailing list can help us out....
> > > >
> > > >The question is: Should you use database level constraints to enforce
the
> > > >integrity of the database or is the integrity of the database the
> > > >responsibility of the EJB?
> > >
> > > Most definitely yes. Not using a proven mechanism such as database
> > > constraints to enforce constraints in your model to me would be like
not
> > > wearing your seatbelt because you are afraid of wrinkles in your
suite.
> > > Even if you enforce your constraints at the EJB level, why not use the
> > > extra safety that database constraints provide. I would view them on
the
> > > same level as asserts in your code. The only thing I can think of,
that
> > > would be a con is that you might have some extra maintenance work
because
> > > if your model constraints change, the db constraints also have to
change.
> > >
> > > from my personal experience I'm completely pro using db constraints as
> >they
> > > have helped discover numerous bugs in the EJB code in projects I've
been
> > > involved in. at signal7 we use a homegrown code-generation suite that
> > > generates both database definition including constraints and EJB
entity
> > > bean code including relationships and deployment files from a
consistent
> > > model so we don't even have the extra maintenance effort. one
could
> > > argue about using cascading deletes and triggers because they can
cause
> > > problems with EJB caches but just enforcing constraints in a
(relational)
> > > database model has helped us considerably in our projects.
> > >
> > > >My collegues opinion is that it is the responsibility of the EJB to
> >enforce
> > > >the integrity of the data in the database. If you would implement
this in
> > > >constraints in the database then both the EJBs and the database would
> >have
> > > >to know about the integrity rules. Which is duplication of
> >knowledge/logic,
> > > >which is not a good thing.
> > >
> > > it depends, see comment above about maintenance and code generation.
> > >
> > > >At first I agreed with him, but now I have second thoughts:
> > > >- What if the database is used by other (non J2EE) applications? The
> > > >integrity then must be maintained by the database, or should all
> > > >applications be held responsible for the integrity? The latter would
mean
> > > >distributing the reponsibility over multiple applications, which is
not a
> > > >good thing? This would advocate to put the responsibility in the
database
> > > >and define the constraints there.
> > > >- By putting the constraints in the database you enforce that their
is
> >one
> > > >place where the data is consistent. Specific application could add
> > > >additional constraints for that application into their logic, as long
as
> >it
> > > >does not conflict with the data model.
> > > >
> > > >I'm anxious to hear your opinions on this....
> > > >
> > > >Regards,
> > > >
> > > >Gero Vermaas
> > > >
> > >
> > > regards,
> > >
> > > robert
> > >
> > >
> > >
> > >
> > >
> > >
> > > (-) Robert Kr�ger
> > > (-) SIGNAL 7 Gesellschaft f�r Informationstechnologie mbH
> > > (-) Br�der-Knau�-Str. 79 - 64285 Darmstadt,
> > > (-) Tel: 06151 665401, Fax: 06151 665373
> > > (-) [EMAIL PROTECTED], www.signal7.de
> > >
> > >
>
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to
> > > [EMAIL PROTECTED] and include in the body of the message "help".
> > >
> > >
> >
>
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