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Re: [eclipselink-users] Uregntly need help for thesis: Batch reading of collection with lazy OneToOne relation 
Hi Frank,

I am not arguing that downcasting is not a useful feature. In fact, when our JPA 2.0 release is done, I suspect it will be fairly high on the list of the features we consider implementing.

What I am suggesting is that for a performance benchmark to merit including a feature like this the benchmark would have to be a fairly far reaching benchmark - likely a bigger benchmark than one would write as part of a bachelor's thesis. Mario has addressed this question in his previous email.

-Tom

Frank Schwarz wrote: 
Hi Mario,

the query key has to be defined on Partner pointing to Employee instead of
Role. Please have a look at
http://code.google.com/p/oopex/source/browse/trunk/modules/eclipselink1-jpa/src/queries-downcasts/java/oopex/eclipselink1/jpa/queries/DowncastsMain.java#139.
I never tried this for defining Join-Reads/Batch-Reads, though.

@Tom: Using downcasts in queries is, from my point of view, something quite
natural if you design your model in a truly object oriented way. Reiterating
that this feature nobody is needing, does not make disappear. The other
feature, Mario is looking for, might be called "fetch-plans/plans" - as in
the old JDO days ;-). See
http://wiki.eclipse.org/EclipseLink/Development/JPA/NestedFetchGroups, last
item in the open issues list. Also this feature(-request) I see frequently
in projects when there is a CRUD-style rich client.

-- Frank

Meet me at JFS2009 http://www.java-forum-stuttgart.de/


Mario Sandro Schwarz wrote:
I did already try it with a customizer based on the workaround from Doug Clarke "Accessing un-mapped attributes using QueryKey " (http://wiki.eclipse.org/EclipseLink/Development/JPA/QueryDownCast). The role entity class was annotated with this Customizer: