def doreadconflict(self, db, mvcc):
tm1 = transaction.TransactionManager()
conn = db.open(mvcc=mvcc, transaction_manager=tm1)
r1 = conn.root()
obj = MinPO('root')
r1["p"] = obj
obj = r1["p"]
obj.child1 = MinPO('child1')
tm1.get().commit()
# start a new transaction with a new connection
tm2 = transaction.TransactionManager()
cn2 = db.open(mvcc=mvcc, transaction_manager=tm2)
r2 = cn2.root()
self.assertEqual(r1._p_serial, r2._p_serial)
obj.child2 = MinPO('child2')
tm1.get().commit()
# resume the transaction using cn2
obj = r2["p"]
# An attempt to access obj.child1 should fail with an RCE
# below if conn isn't using mvcc, because r2 was read earlier
# in the transaction and obj was modified by the other
# transaction.
obj.child1
return obj
