Yeah, in 3.0 EJBQL is somewhat of an implant from the JPA world, so it
lacks a few Cayenne conveniences. I am certainly in favor to add
support for "db:" expressions in the future versions (and the patches
are welcomed).
For now the option is to map PK column as the object property. Other
than exposing it to the world, this shouldn't have any side effects.
Auto generation will still work, etc.
Andrus
On Dec 4, 2009, at 12:05 AM, Dave Lamy wrote:
Hello all--
I am curious to know how (if possible) to reference a PK field using
EJBQL.
I tried using the normal expression "db:" syntax but as I saw in the
source
this won't work. EJBQLPathTranslator.processLastPathComponent()
appears to
assume that the last part of any path will reference either an
ObjAttribute
or an ObjRelationship, and will throw an IllegalStateException if
neither of
these are the case.
I'd like to have access to the PK field for a couple of purposes.
One, when
doing COUNT queries it is faster to do a COUNT(PK) than a COUNT(*).
Furthermore, I want to be able to essentially group aggregate function
results by objects, which would be impractical to do using the
OBJECT(e)
notation, so the plan was to perform the group query using IDs and
then fill
in the results with objects on the way out.
Since the call from processLastPathComponent() to
processTerminatingAttribute() just resolves into a DbAttribute and
thus a
column name anyway, wouldn't it be rather simple patch to do a "db:"
check
on the path component and presume a DB column name instead of an
ObjAttribute name? I imagine I may be oversimplifying the
situation, but if
not and there is agreement on the method I don't mind doing the patch.
Of course, if there is an alternative way to reference PKs that I'm
unaware
of please enlighten me :-).
Thanks--
Dave
