I've followed the ODMG work since Versant 1.0 and am familiar with some of these
initiatives. As you know Rick Cattell from Sun has pushed the Relational World towards
the ODMG spec with JDBC 2.0 Java Blend etc. and although not totally familiar, SQL3 and OQL are very close.
When speaking with David Jordan at the last JavaOne, it seems that the
ObjectBase
people still don't want totally compilant to ODMG and he has done alot
of work to make the
ODMG spec more flexible with higher performance. Of course, we see
the same thing with
all the proprietary stuff from the relational vendors. I had the opportunity
to work with Poet's
enbedded Java ObjectBase Navajo and the new ODMG spec is much
better and cleaner.
What we really need is something like an ODMG interface with CMP since
the ObjectBases
really do everything that's needed. CMP with Relational and trying
to create unique keys
is such a pain. I really don't have a solution wanted to put my two
cents in. I think this group
has a good chance at driving this effort based on the Free Software
model. Or maybe JDO
is a good option, I'll have to check it out.
Thanks,
eric :-)
Alexandre Lefebvre wrote:
Thanks for the pointer!
We are aware of the work around JDO, and also have a relationship with Versant.alex
Jim Baiter wrote:
You might also want to follow the Java Data Objects (JDO)
spec at Sun. I recently attended a seminar at the Silicon
Valley Java Users Group where a rep from Versant was discussing
this. It sounds very similar to what you are mentioning below.>From: Alexandre Lefebvre <[EMAIL PROTECTED]>
>Reply-To: [EMAIL PROTECTED]
>To: "'[EMAIL PROTECTED]'"
><[EMAIL PROTECTED]>
>Subject: Re: Question re: CMP, JEntityHome, JBeanEntity implementation
>Date: Fri, 05 May 2000 10:15:52 +0000
>
>Yes, the current version of JOnAS is not optimized.
>
>The first query, which corresponds to the findByPrimaryKey, is about
>verifying that the identifiers (PK) are valid.
>The second query is issued when a business method is called, in order for
>the container to load the objet attributes into main memory.
>
>France Telecom R&D is currently working on an adaptable persistence layer
>for Java objects called JORM (Java Object Repository Mapping).
>JORM will be integrated in a future version of JOnAS, in order to provide
>enhanced CMP (including persistent inter-bean references and polymorphism
>of entity beans).
>
>The plan is then to develop a caching mechanism (see also Adam McClure's
>reply to this message) on top of JOnAS + JORM. This cache would indeed
>limit the waste of resources.
>
> alex
>
>Bryan Field-Elliot wrote:
>
> > We use CMP beans extensively, and I am examing the code generated by
>GenIC
> > for "JOnAS###Bean###Home" and "JOnAS###Bean###" (where ### is the name
>of my
> > bean). This is the code which implements the JEntityHome and JBeanEntity
> > interfaces.
> >
> > It seems that _two_ queries get issued for every finder method, but it
>seems
> > to me that the job can be done with only one. This is a big performance
> > problem for us, and would be a great performance boost if we could make
>it
> > into one query.
> >
> > For example, if I have a table called "Employees" with a primary key
>"id"
> > and other fields "name" and "job", then a findByPrimaryKey(100) would
>result
> > in the following two queries:
> >
> > select Employees.id from Employees where Employees.id=?
> > select Employees.id, Employees.name, Employees.job from Employees where
> > Employees.id=?
> >
> > The first is issued by the Home interface implementation
> > (pkFindByPrimaryKey), and the second is implemented by the Bean
> > implementation (loadData).
> >
> > As far as I can see, the first query is a big waste of resources, and
>pretty
> > much cuts performance in half. I don't understand why the first query is
> > executed at all, since it's function (to check whether or not the row
> > exists) can be performed by the second query just as well.
> >
> > Can someone please explain why it works this way, and if possible, how
>to
> > optimize it?
> >
> > Thank you,
> > Bryan
> >
> >
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