Weird problem with a query only returning valid data for the first time, but not for the second!

[Dominik Stadler]

Hi,

I have a problem in my application where a query that sometimes returns data
and sometimes not.

I have reduced it to the code as much as I could into an Eclipse project
available at http://ubuntuone.com/p/S9n/

This uses OpenJPA 2.0.1 and a out-of-process Derby database.

Basically I have two Entities which both use multiple Ids to produce the
Primary Key, "Preis" contains a foreign key on "Website":

@Entity
@IdClass(MandantAndNameIdentity.class)
public class Website {
    @Id
    private String mandant;

    @Id
    private String name;
...
}

@Entity
@IdClass(WebsiteProduktDatumIdentity.class)
public class Preis {
    @Id
    @ManyToOne(cascade = CascadeType.MERGE)
    private Website website;

    @Id
    @Basic
    private String datum;
...
}

I use the following to set up a website and a Preis:

        em.getTransaction().begin();

        Website website = em.merge(new Website("Mandant", "Website"));

        em.merge(new Preis(website, DATUM));

        em.getTransaction().commit();

Afterwards, if I run the query as follows:

       TypedQuery<Preis> q = em.createQuery(
                "select m from Preis m " +
                "where m.website.name = :website ", Preis.class);
       q.setParameter("website", website.getName());

this query works all the time, note that it uses website.name for matching,
not the full Website-object.

However if I put the query as

        TypedQuery<Preis> q = em.createQuery(
                "select m from Preis m " +
                "where m.website = :website ", Preis.class);
        q.setParameter("website", website);

it only works ONCE and then does not return any results any more!! See
testcase DataAccessVerifyTest for details.

Is this a dummy dumb user error? Or do I miss something basic in JPA? Or is
this in fact a misbehavior of OpenJPA?

Thanks... Dominik.