On Aug 7, 2007, at 12:11 PM, Andy Jefferson wrote:
With this restriction in place, however, would I be able to do the
following?
// fetch a detched object
Query q = pm.newQuery(Foo.class);
q.setUnique(true);
Foo foo = (Foo) q.execute();
"detachAllOnCommit" will transition instances to detached *at
commit*. You
have no commit here (using nontransactionalRead ?). If you have
tx.begin(),
tx.commit() around it then its definitely fine. Nothing in the spec
definition of "detachAllOnCommit" implies (to me) that queries run
with
non-tx read will do the detach.
Sorry - my bad. I meant to wrap the above in a transaction, thus
detaching the enlisted foo instance.
// make it dirty:
foo.setBar("bar");
"foo" : detached-clean -> detached-dirty
// attach
pm.currentTransaction().begin();
pm.makePersistent(foo);
"foo" : detached-dirty -> persistent-clean
pm.currentTransaction().commit();
"foo" : persistent-clean -> detached-clean
// dirty it once more
foo.addBaz("baz");
"foo" : detached-clean -> detached-dirty
// and attach it a second time
"foo" : detached-dirty -> persistent-clean
I'm with you until this last one... It would transition from
persistent-clean to detached-clean upon committing the transaction,
right? If so, then we're aligned...
- wouldn't this cause the JDOUserException you mention above?
No. If referring to the same PM, the object would have been removed
from L1
cache at detach. The exception I was referring to was if you did a
separate
PM.detachCopy() or detached it from a different PM and *then* tried
to attach
to the same PM as one that already had it.
Aha.. not knowing how the L1 cache really works, I didn't know that
instances get evicted on detach. This would work, it seems. More to
the point, my application uses a new PM for each successive
makePersist() call, so there's even less chance of the instance
already existing in the L1 cache.
Sounds like we're on the right track...
- Chris
