Re: JDO comparisons

Robert Klemme <robert.klemme_at_myview.de> wrote in message news:<3C7519AF.8C529479_at_myview.de>...
> hi eric!
>
> Eric Samson schrieb:
> >
>
> > 2 or 3 RDBMS columns can "look like" a Java Collection if you have
> > something like JDO, otherwise it will mostly remain "conceptual".
>
> yes, of course this depends on the usage.
>
> > It seems that you consider SQL as a programming language.
>
> not at all. i was just thinking about the task to find an object
> or several objects that satisfy a certain criterion that involves
> members of a collection. when coding an application that
> accesses relational database tables you would of course use SQL
> to get your hands at the entries. on the other hand you would
> have to use JDO QL when you are working with JDO - unless you
> want to instantiate some (possibly huge) collection and search in
> memory.
>
> > For me SQL
> > is well-suited and has been designed for ad-hoc queries outside
> > applications.
>
> i don't have a statistic at hand but my guess is that the sheer
> number of applications that use regularly SQL inside proves its
> fitness for in-application usage.
>
> > JDO QL aim is only to simply identify entry points from which you'll
> > be able to transparently navigate in pure Java. So in JDO queries are
> > less
> > JDO QL does not pretend to be an ad-hoc query language.
>
> if you look at it from this point of view you are right. the
> downside of this is that you must materialize your data in memory
> which can be a serious drawback.
>
> > Anyway, a JDO implementation is free to optionally support SQL in
> > addition to JDO QL support. This is exaclty what LiDO, our product
> > does.
>
> hm, sounds like you admit the shortcomings of JDO QL by including
> SQL support into the product... :-)
>
> regards
>
> robert
>
> --
>
> Robert Klemme
> Software Engineer
> -------------------------------------------------------------
> myview technologies GmbH & Co. KG
> Riemekestra? 160 ~ D-33106 Paderborn ~ Germany
> E-Mail: mailto:robert.klemme_at_myview.de
> Telefon: +49/5251/69090-321 ~ Fax: +49/5251/69090-399
> -------------------------------------------------------------

Hi Robert

Many of our customers and prospects are requesting direct SQL (and Compiled Query) support. If they don't have portability issue, then it's OK for me to let them tuning their SQL queries by themselves. It mostly concerns very big queries with complex WHERE clauses, where any SQL optimizer gives up.

I think that JDO QL is not as object-oriented as Carl Rosenberg would like, and less complete than SQL for ah-hoc queries. But it EXISTS, it's fully portable (our implementation supports RDBMS, ODBMS and flat files), it supports inheritance and navigation through references and collections.

So you can use JDO QL to get a root object, from which you will navigate in pure Java. Then with LiDO, if RDBMS is the only target, you can use SQL or compiled queries when you need complex queries.

I think this is a reasonable mix.

Best Regards, Received on Fri Feb 22 2002 - 10:26:16 CET