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From "Patrick Linskey" <plins...@bea.com>
Subject RE: possible to write a JPA Query to that filters both an Entity and its relationship entities?
Date Sat, 24 Feb 2007 00:36:44 GMT
I would expect that your query would return the unfiltered employees
collection. But I have not run any tests.

In other words, I would expect that the oldtimers collection would be
the full set of employees for each dept that had any oldtimers >= 15.

That said, I don't think that your interpretation is necessarily wrong.
Just not my expectation.

-Patrick

-- 
Patrick Linskey
BEA Systems, Inc. 

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> -----Original Message-----
> From: Craig.Russell@Sun.COM [mailto:Craig.Russell@Sun.COM] 
> Sent: Friday, February 23, 2007 4:14 PM
> To: open-jpa-dev@incubator.apache.org
> Subject: Re: possible to write a JPA Query to that filters 
> both an Entity and its relationship entities?
> 
> Hi Patrick,
> 
>  From the JPQL
> select dept, oldtimers from Department dept LEFT JOIN  
> dept.employeeCollection oldtimers WHERE dept.deptno >= 100 AND   
> oldtimers.yearsOfService >= 15
> 
> I expect to get SQL that looks something like
> select dept.id, dept.name, oldtimers.id, oldtimers.firstname,  
> oldtimers.lastname, oldtimers.salary, oldtimers.ssn from Department  
> dept, Employee oldtimers WHERE dept.id = oldtimers.deptid AND  
> dept.deptno >= 100 AND  oldtimers.yearsOfService >= 15
> 
> I then construct instances from the returned dept and oldtimers  
> columns and give back to the user the results, with one result row  
> for each SQL ResultSet row. So the filtering from the JPQL 
> translated  
> into the WHERE clause in the SQL should exclude oldtimers that don't  
> qualify.
> 
> If you don't use the oldtimers.yearsOfService >= 15 in the SQL, then  
> you will get all of the employees in the department returned in the  
> result. But why do you not use the oldtimers.yearsOfService >= 15 in  
> the SQL?
> 
> Craig
> 
> On Feb 23, 2007, at 2:12 PM, Patrick Linskey wrote:
> 
> >> In fact, you have to do a bit of work to get SQL to return you non-
> >> filtered instances. So I don't get it. Does OpenJPA not
> >> construct the
> >> obvious SQL that filters oldtimers?
> >
> > I don't think that you and I are really in sync here. Maybe 
> some more
> > concrete examples are in order?
> >
> > -Patrick
> >
> > -- 
> > Patrick Linskey
> > BEA Systems, Inc.
> >
> > 
> ______________________________________________________________
> ________ 
> > _
> > Notice:  This email message, together with any attachments, may  
> > contain
> > information  of  BEA Systems,  Inc.,  its subsidiaries  and   
> > affiliated
> > entities,  that may be confidential,  proprietary,  copyrighted   
> > and/or
> > legally privileged, and is intended solely for the use of the  
> > individual
> > or entity named in this message. If you are not the intended  
> > recipient,
> > and have received this message in error, please immediately return  
> > this
> > by email and then delete it.
> >
> >> -----Original Message-----
> >> From: Craig.Russell@Sun.COM [mailto:Craig.Russell@Sun.COM]
> >> Sent: Friday, February 23, 2007 2:09 PM
> >> To: open-jpa-dev@incubator.apache.org
> >> Subject: Re: possible to write a JPA Query to that filters
> >> both an Entity and its relationship entities?
> >>
> >> So,
> >>
> >> I can tell you that having a result column that is filtered in the
> >> query is not what a user would expect. In JDO, the oldtimers column
> >> would be filtered.
> >>
> >> In fact, you have to do a bit of work to get SQL to return you non-
> >> filtered instances. So I don't get it. Does OpenJPA not
> >> construct the
> >> obvious SQL that filters oldtimers?
> >>
> >> I've re-read the JPA specification, and it appears to be silent on
> >> the issue of filtering. Is this a portability issue?
> >>
> >> Craig
> >>
> >> On Feb 23, 2007, at 1:57 PM, Tom Mutdosch wrote:
> >>
> >>> Hi Patrick,
> >>> Thanks for the query suggestion.  I guess what I was initially
> >>> thinking of doing was incorrect in that JPA doesn't really give me
> >>> a "view" of what I want.  That is, I can never get a Department
> >>> object containing a list of filtered Employees.  A JPA object
> >>> returned from a query is always going to be an exact
> >> representation
> >>> of the database.  So your Department object is always going to
> >>> contain all of the Employees in its relationship.
> >>>
> >>> So like you mentioned, I can still get all the information using
> >>> one query, and then just process those results as I want them.  I
> >>> imagine that this would entail some sort of wrapper bean
> >> that would
> >>> house the Department and the filtered list of Employees.  Or what
> >>> if I added a regular method to my Department entity called
> >>> getFilterEmployees() which would return a List that I populated
> >>> with the filtered results from my query?  Does that seem like a
> >>> reasonable thing to do -- if I didn't want to deal with a wrapper
> >>> object but still have all of my desired data captured by a single
> >>> Entity?
> >>> Thanks
> >>> Tom
> >>>
> >>>
> >>> Patrick Linskey wrote:
> >>>> It is, but it doesn't buy you much in this situation --
> >> the oldTimers
> >>>> collection in your example won't be filtered to just the
> >> ones that
> >>>> are
> >>>> old. It'll be all the employees in the dept.
> >>>>
> >>>> -Patrick
> >>>>
> >>>>
> >>
> >> Craig Russell
> >> Architect, Sun Java Enterprise System 
> http://java.sun.com/products/ 
> >> jdo
> >> 408 276-5638 mailto:Craig.Russell@sun.com
> >> P.S. A good JDO? O, Gasp!
> >>
> >>
> 
> Craig Russell
> Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
> 408 276-5638 mailto:Craig.Russell@sun.com
> P.S. A good JDO? O, Gasp!
> 
> 

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