Hibernate is not deleting my objects. Why?

Question

I have just set up a test that checks that I am able to insert entries into my database using Hibernate. The thing that drives me crazy is that Hibernate does not actually delete the entries, although it reports that they are gone!

The test below runs successfully, but when I check my DB afterwards the entries that were inserted are still there! I even try to check it using assert (yes I have -ea as vm parameter). Does anyone have a clue why the entries are not deleted?

public class HibernateExportStatisticDaoIntegrationTest {
    HibernateExportStatisticDao dao;
    Transaction transaction;

    @Before
    public void setUp(){
        assert numberOfStatisticRowsInDB() == 0;
        dao = new HibernateExportStatisticDao(HibernateUtil.getSessionFactory());
    }

    @After
    public void deleteAllEntries(){
        assert numberOfStatisticRowsInDB() != 0;
        Session session = HibernateUtil.getSessionFactory().getCurrentSession();
        for(PersistableStatisticItem item:allStatisticItemsInDB()) {
            session.delete(item);
        }
        session.flush();
        assert numberOfStatisticRowsInDB() == 0;
    }

    @Test public void exportAllSavesEntriesToDatabase(){
        int expectedNumberOfStatistics = 20;
        dao.exportAll(StatisticItemFactory.createTestStatistics(expectedNumberOfStatistics));

        assertEquals(expectedNumberOfStatistics, numberOfStatisticRowsInDB());
    }

    private int numberOfStatisticRowsInDB() {
        return allStatisticItemsInDB().size();
    }

    @SuppressWarnings("unchecked")
    private List<PersistableStatisticItem> allStatisticItemsInDB(){
        Session session = HibernateUtil.getSessionFactory().getCurrentSession();
        transaction = session.beginTransaction();
        Query q = session.createQuery("FROM PersistableStatisticItem item");
        return q.list();
    }
}

The console is filled with

Hibernate: delete from UPTIME_STATISTICS where logDate=? and serviceId=?

but nothing has been deleted when I check it.

Answer 1

I guess it's related to inconsistent use of transactions (note that beginTransaction() in allStatisticItemsInDB() is called several times without corresponding commits).

Try to manage transactions in proper way, for example, like this:

Session session = HibernateUtil.getSessionFactory().getCurrentSession();
Transaction tx = session.beginTransaction();
for(PersistableStatisticItem item:
    session.createQuery("FROM PersistableStatisticItem item").list()) {
    session.delete(item);
}
session.flush();
assert session.createQuery("FROM PersistableStatisticItem item").list().size() == 0;
tx.commit();

See also:

• 13.2. Database transaction demarcation

Answer 2

I have the same problem. Although I was not using transaction at all. I was using namedQuery like this :

Query query = session.getNamedQuery(EmployeeNQ.DELETE_EMPLOYEES);
int rows = query.executeUpdate();
session.close();

It was returning 2 rows but the database still had all the records. Then I wrap up the above code with this :

Transaction transaction = session.beginTransaction();
Query query = session.getNamedQuery(EmployeeNQ.DELETE_EMPLOYEES);
int rows = query.executeUpdate();
transaction.commit();
session.close();

Then it started working fine. I was using SQL server. But I think if we use h2, above code (without transaction) will also work fine. One more observation : To insert and get records usage of transaction is not mandatory but for deletion of records we will have to use transaction. (only tested in SQL server)

Answer 3

Can you post your DB schema and HBM or Fluent maps? One thing that got me a while back was I had a ReadOnly() in my Fluent map. It never threw an error and I too saw the "delete from blah where blahblah=..." in the logs.