Hey guys,
I am in the middle of porting the Apache Jetspeed Portal from OJB to JPA
and JTA using Spring and Extended EntityManagers. I am using the
released version of JPA, OpenJPA 1.2.0. So far so good, but I do have a
question concerning eviction from the query cache: if I have a
relationship between two objects that is manifest only in JPQL
statements, will inserts against one object table clear a query cache
that contains results for the other object?
Here is a more detailed description of the situation.
@Entity
@NamedQuery (name="ABA", query="select a from A a, B b, A a2 where a2.name = :name
and a2.id = b.id0 and b.id1 = a.id")
Class A
{
@Id
private Long id;
@Basic
private String name;
...
}
@Entity
Class B
{
@Id
private Long id0;
@Id
private Long id1;
...
}
Note the NamedQuery is the only relationship between class A and B Open
JPA could be aware of since there are no *ToMany or *ToOne declared.
Here is what I am observing based on trace logging:
1. Query for a list of A using query ABA and get no results, (OpenJPA
generates and executes a correct select SQL),
2. Persist a new instance of B such that the original query should be
satisifed, (OpenJPA generates and executes the corresponding insert
SQL), and
3. Reissue the original query for a list of A using query ABA:
unexpectedly returns no results, (OpenJPA indicates a cache hit and no
SQL is logged).
I can easily imagine that OpenJPA would not automatically find and
maintain this programmatic relationship between A and B. However, the
documentation on query cache eviction seems to claim it might because
clearly B is in the "access path" of A based on the ABA query.
Consequently, it claims query results for A would have been cleared by
the insert of a B instance.
No doubt there are work arounds here including manual eviction based on
class A and I am going to start experimenting to find the one that works
best in this case. I am also going to look into using the 'timestamp'
eviction policy to see if that helps. I am posing the question though to
make sure I am not totally in left field. I assume that if I actually
modeled the relationships between A and B explicitly, I would not have
run into this behavior, correct?
Thanks for the assistance/clarification in advance,
Randy Watler
Jetspeed2 Committer
