[jira] Commented: (OPENJPA-265) datacache does not get committed when application commit after a query

["Patrick Linskey (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OPENJPA-265?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12507808 ] 

Patrick Linskey commented on OPENJPA-265:
-----------------------------------------

> If datacache is not committed, another transaction does not see
> the loaded data in the data cache and will redundantly query the database again.

To follow up: since DataCache.commit() is poorly named, and the data cache is non-transactional, the data loaded during one transaction will be available to other transactions immediately. So, the data cache is somewhere between a READ_COMMITTED and REPEATABLE_READ, semantically. The only exception is if direct JDBC work is performed on the data source before OpenJPA reads data from the database; in these situations, cache population may be turned off by calling OpenJPAEntityManager.setPopulateDataCache(false).

> 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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