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https://issues.apache.org/jira/browse/OPENJPA-265?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Patrick Linskey resolved OPENJPA-265.
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Resolution: Invalid
OpenJPA's data cache implementation as currently implemented is updated outside
the bounds of the transaction. As such, it is not an XA resource, and does not
participate in the transaction per se. It receives notifications of committed
data during an afterCompletion() callback.
Since the cache never receives updates until after a transaction has
successfully completed, there is no opportunity for the cache to be populated
with invalid data. However, since the cache update is not part of the commit
itself, it is possible for a cache to have stale data, if somehow an exception
is raised between the commit to the database and the cache update logic. Since
the OpenJPA cache is designed primarily for the optimistic transaction model,
and the cache already handles self-healing in the face of optimistic
transaction failures and stale data, this increased staleness opportunity is
unfortunate but not fatal.
It would be possible to change the current implementation (or create a new
implementation) that is transactional. However, there is a significant
additional cost to doing this, as all transactions would then need to be XA
transactions. Further, OpenJPA would be taking up two XA slots, meaning that
the two-resource XA optimization would not be available if any other data
sources were added to the XA tx.
DataCache.commit() would be better-named DataCache.notifyOfCommit().
> datacache does not get committed when application commit after a query
> ----------------------------------------------------------------------
>
> Key: OPENJPA-265
> URL: https://issues.apache.org/jira/browse/OPENJPA-265
> Project: OpenJPA
> Issue Type: Bug
> Components: datacache
> Affects Versions: 1.0.0
> Reporter: Daniel Lee
>
> I'm that sure whether this is a bug or not but what is observed is that the
> application commit in the following code does not trigger commit on the
> datacache.
> =============================================================
> EntityManagerFactory emf = Persistence.createEntityManagerFactory("demo");
> EntityManager em = emf.createEntityManager();
> em.getTransaction().begin();
> Customer c = (Customer) em.createQuery("select c from Customer c where
> c.name='Harry Auto'").getSingleResult();
> em.getTransaction().commit();
> =============================================================
> Is this normal because there is no update? It make sense that there is no
> need to flush on the database, but the datacache has been newly loaded with
> the customer "Harry Auto" and the objects that are eagerly related to "Harry
> Auto". If datacache is not committed, another transaction does not see the
> loaded data in the data cache and will redundantly query the database again.
> Is this a bug or working as design? Many thanks.
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