public void concUpdate(ExtObjectContainer oc, int seq) throws Exception {
   Query q = oc.query();
   q.constrain(IndexedByIdentityTestCase.class);
   ObjectSet os = q.execute();
   Assert.areEqual(COUNT, os.size());
   while (os.hasNext()) {
     IndexedByIdentityTestCase idi = (IndexedByIdentityTestCase) os.next();
     idi.atom.name = "updated" + seq;
     oc.store(idi);
     Thread.sleep(100);
   }
 }
  public void concDelete(ExtObjectContainer oc) throws Exception {
    int size = countOccurences(oc, SimpleObject.class);
    if (size == 0) { // already deleted
      return;
    }
    Assert.areEqual(ELEMENT_COUNT, size);

    ObjectSet os = oc.query(ArrayItem.class);
    if (os.size() == 0) { // already deteled
      return;
    }
    Assert.areEqual(1, os.size());
    ArrayItem item = (ArrayItem) os.next();

    // waits for other threads
    Thread.sleep(500);
    oc.delete(item);

    oc.commit();

    assertOccurrences(oc, SimpleObject.class, 0);
  }
 public void conc1(ExtObjectContainer oc) throws Exception {
   ObjectSet os = oc.query(Item.class);
   Thread.sleep(500);
   deleteObjectSet(oc, os);
   oc.rollback();
 }
 public void conc2(ExtObjectContainer oc) throws Exception {
   ObjectSet os = oc.query(Item.class);
   Thread.sleep(500);
   deleteObjectSet(oc, os);
   assertOccurrences(oc, Atom.class, 0);
 }