SQLAlchemy: Why I raise HTTPFound will cause no data be inserted into database?

Question

I built a view which allow user input some information and inserted that information as a new record into my database with Pyramid framework. The code is like this:

def orderplace_view(request):
    user = User.get(authenticated_userid(request))
    cart = Cart.get_by_user(user)

    if cart.itemtypes == None:  # cat is empty
        request.session.flash(u'Empty cart')
        raise HTTPFound(location = request.route_url('cart'))

    placeorderform = PlaceOrderForm(request.POST)
    placeorderform.address.query = UserAddress.query_by_user(user)

    if request.POST and placeorderform.validate():
        # create order
        order = Order()
        order.address = placeorderform.address.data

        # fill order with other attributes...
        user.orders.append(order)

        # IMPORTANT LINE!!!
        raise HTTPFound(location = request.route_url('order_list'))

    return {'user': user,
        'title': 'place order',
        'cart': cart,
        'placeorderform': placeorderform}

Here's the strange thing: If I commented out the "raise HTTPFound()" line, everything works fine, a new order would be inserted into database. But if I keep that line which redirect user to Order List page, the order won't be inserted! Why this happened?

rkhayrov rkhayrov · Accepted Answer · 2012-09-26T05:10:34

If Pyramid transaction middleware is in use, it will abort the containing transaction when view function raises an exception: http://docs.pylonsproject.org/projects/pyramid_tm/en/latest/#transaction-usage

Commit explicitly with transaction.commit(), or, better yet, return HTTPFound instead of raising it.

SQLAlchemy: Why I raise HTTPFound will cause no data be inserted into database?

1 Answers