NHibernate等效于SQL“ UPDATE table SET column = column +…”

Question

I'm trying to update Quantity of a Product in a sale system using NHibernate.

        using (var session = NHibernateSessionUtil.OpenSession())
        {
            using (var trans = session.BeginTransaction())
            {
                var product = session.Load<Product>(1);
                product.Quantity += 2;
                session.SaveOrUpdate(product);
                trans.Commit();
            }
        }

However, NHibernate will generate an SQL in this form:

        UPDATE Product SET quantity = 2 WHERE id = 1;

If another client updates product quantity while this code is processing, the quantity will be incorrect . The solution I can think of so far is to lock that row before making the update:

                ...
                var product = session.Load<Product>(1);

                // lock row for update
                session.Lock(product, LockMode.Upgrade);

                product.Quantity += 2;
                session.SaveOrUpdate(product);
                ...

However, this can affect other client if I need to update a long list of products.

Is there an equivalent method in NHibernate to generate SQL like:

    UPDATE Product SET quantity = quantity + 2 WHERE id = 1;

?

any suggestion?

Update

I've tried opening session with serializable isolation level as @Fran suggested:

    ...
    using (var trans = session.BeginTransaction(IsolationLevel.Serializable))
    ...

The problem is when the row is modified by another client before this transaction is committed, an exception occurs:

    {"ERROR: 40001: could not serialize access due to concurrent update"}

does that mean we need to explicitly lock every row that need updating? ie:

    var product = session.Load<Product>(1, LockMode.Upgrade);

if the locking is necessary, what is the different between opening transaction with and without IsolationLevel.Serializable ?

Answer 1

the only way I see doing this is locking the object in a serializable transaction.

so when you open your transactions give it an Isolation level of serializable. This will lock the object until you commit the transaction.