hi scott,
this is it:
crit = new Criteria();
crit.addOrderByDescending("id");
crit.addOrderByAscending("geburtsDatum");
crit.addPrefetchedRelationship("konti"); <<<<<<<<<<<<<<
query = new QueryByCriteria(Person.class, crit);
it's also described in query.html in the docs.
hth
jakob
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: "OJB Users List" <[EMAIL PROTECTED]>
Sent: Wednesday, September 25, 2002 3:14 PM
Subject: Re: Re: Possible PB enchanement
> Great News.. I will look through the docs(although belive me I have
already poored over them) and find out how to user query prefetching...
>
> Thanks,
> Scott
> >
> > From: Thomas Mahler <[EMAIL PROTECTED]>
> > Date: 2002/09/25 Wed AM 02:16:42 EDT
> > To: OJB Users List <[EMAIL PROTECTED]>
> > Subject: Re: Possible PB enchanement
> >
> > You are lucky,
> >
> > this is already implemented. We called this feature query prefetching.
> >
> > cheers,
> > Thomas
> >
> > Scott Shealy wrote:
> > > I was looking through the toplink api and they have a really nice
> > > feature that really speeds up the performance of some queries when you
> > > know you are going to access some of the children objects by going
ahead
> > > and loading them at initial query time.
> > >
> > > See the reference to the feature for this at (I think you have to have
a
> > > technet id but maybe not)
> > >
http://technet.oracle.com/docs/products/ias/doc_library/90200doc_otn/toplink
.903/b10064/performa.htm#1025931
> > >
> > >
> > > So for instance say you have 2 objects Item and Group
> > >
> > > Item has as a member exacty one group.
> > >
> > > Currently(at least with my limited knowledge of OJB) with a query by
> > > collection you would generate N + 1 SQL statements. One for the query
> > > of the Item Collection and one subsequent query to retrieve the Group
> > > for each Item returned by the Query. It would be nice if you could
> > > specify ahead of time that you wanted to go ahead and load both in the
> > > same query. So a SQL statement like this would generated ...
> > >
> > > SELECT item.col1,item.col2,group.col1,group col2
> > > FROM item INNER JOIN group on group.group_id = item.group_id,
> > >
> > > This would really be a performance enhancement when you know you are
> > > going to accessing the group ahead of time.
> > >
> > > In the top link api they use the following syntax to indicate that
they
> > > want to load the attribute in oneQuery,
> > >
> > > query.addJoinedAttribute("group.col2");
> > >
> > > Then the persistence layer is able to examine that and know what to
do.
> > >
> > > How would hard would this be to do for OJB?
> > >
> > > The toplink API is also able to handle loading children collections in
> > > two queries using a select distinct sql statement after loading the
> > > initial collection .
> > >
> > > I hope this made sense, if not please read the TOPLINK docs cause it
> > > does a much better job of explaining this than me..
> > >
> > > This feature would be really nice...
> > >
> > > Scott
> > >
> > >
> > >
> > >
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> > >
> > >
> > >
> >
> >
> >
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