Re: [eclipselink-users] Uregntly need help for thesis: Batch reading of

[Mario Sandro Schwarz <mario.sandro.schwarz@xxxxxx>]

Hello Tom,

unfortunately the problem is that not the role has the "bankaccount". 
Just the specific role "employee" does.
I remember you replying to my last post telling me that there is a an 
open enhancement request for this kind of thing (Downcasting in 
queries). Thanks a lot for the try to help though.

Anyone got any other suggestions that might help?

Mario


Tom Ware schrieb:
> EclipseLink allows multi-level fetch joins and batch reading.  Have 
> you tried any of these?
>
> http://wiki.eclipse.org/Using_EclipseLink_JPA_Extensions_%28ELUG%29#Join_Fetch 
>
>
> (something like @QueryHint(name = QueryHints.LEFT_FETCH, value = 
> "p.roles.bankAccount")
>
> http://wiki.eclipse.org/Using_EclipseLink_JPA_Extensions_%28ELUG%29#Batch
>  (something like @QueryHint(name=QueryHints.BATCH, 
> value="p.roles.bankAccount");
>
> Mario Schwarz wrote:
> > Hi everybody.
> >
> > I have to do a run time comparison on Eclipselink and Hibernate for 
> > my Bachelor Thesis. I really have an urgent problem, I don't get 
> > BatchReading to work correctly.
> >
> > I implemented use-case based test cases that call specific methods of 
> > a  SessionBean called "PartnerService". PartnerService acts as a 
> > Facade and manages the transactions 
> > (@TransactionAttributeType.REQUIRED). It calls methods on a DAO 
> > called "PartnerDAO". PartnerDAO requires an open transaction 
> > (@TransactionAttributeType.MANDATORY)
> >
> > I have the following NamedQuery which retrieves me all partners with 
> > their addresses and their roles:
> >
> > @NamedQuery(name = "getAllPartnersWithAdressesAndRoles", query = 
> > "SELECT p FROM Partner as p ", hints = {
> > @QueryHint(name = QueryHints.LEFT_FETCH, value = "p.roles"),
> > @QueryHint(name = QueryHints.LEFT_FETCH, value = "p.addresses"),
> > @QueryHint(name = QueryHints.JDBC_FETCH_SIZE, value = "1000") })
> >
> > Now I also want to retrieve the bank account of the specific role 
> > "employee"  which is a unidirectional onetoone-relation. In the 
> > PartnerDAO-method I do the following:
> >
> > public List<Partner> findAllPartners() {
> >   Query q = em.createNamedQuery("getAllPartnersWithAdressesAndRoles");
> >   // results in just 1 SELECTs
> >   List<Partner> l = q.getResultList();
> >   for (Partner partner : l) {
> >     for (Role role : partner.getRoles()) {
> >       // results in l.size() SELECTs
> >       BankAccount ba = ((Employee) role).getBankAccount();
> >     }
> >   }
> > }
> >
> > My goal is to iterate over all roles and retrieve all BankAccounts in 
> > a single SELECT. I guess the problem is, that BankAccount has no 
> > ForeignKey of its Employee. With Hibernate it works though. Oh, by 
> > the way, I am not able to change the mapping to bidirectional anymore!
> >
> > Any help is more than appeciated!
> > Thanks
> > Mario 
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