Calling transaction.commit() inside commit_on_success block in Django

Question

I have code like:

@transaction.commit_on_success()
def foo():
    # Performs various database operations and may raise exception
    do_stuff()

    my_object = MyModel.objects.create()

    # Commit transaction so Celery task will see the newly created object
    transaction.commit()

    # Async call Celery task that does something with the new object
    my_celery_task.delay(my_object.id)

Does this do what I expect it to do, ie:

• If no exceptions occur, transaction.commit() performs commit
• If do_stuff() raises exception, transaction is rolled back

I'm on Django 1.4 and MySQL.

Answer 1

Yes. According to Django docs:

If the function returns successfully, then Django will commit all work done within the function at that point. If the function raises an exception, though, Django will roll back the transaction.

From here

Answer 2

transaction.commit_on_success() will commit if the view returns normally, and abort if an exception is raised. In your case, it should "work" but is possibly not the best solution - since you have to manually commit anyway, you'd probably be better using transaction.commit_manually() ( https://docs.djangoproject.com/en/1.4/topics/db/transactions/#django.db.transaction.commit_manually ):

@transaction.commit_manually()
def foo():
    try:
        # Performs various database operations and may raise exception
        do_stuff()
        my_object = MyModel.objects.create()

    except Exception, e:
        # oops, let's forget about it
        transaction.rollback()
        raise

    else:
        # Commit transaction so Celery task will see the newly created object
        transaction.commit()
        # Async call Celery task that does something with the new object
        my_celery_task.delay(my_object.id)