python - 在 Django 中控制原子事务

Question

我有一个简单的图书馆应用程序。为了强制将 3 个操作作为一个操作提交，并在任何操作失败时回滚，我进行了以下代码更改:

在 settings.py 中:

AUTOCOMMIT=False

在forms.py

from django.db import IntegrityError, transaction
    class CreateLoan(forms.Form):
        #Fields...
        def save(self):
            id_book = form.cleaned_data.get('id_book', None)
            id_customer = form.cleaned_data.get('id_customer', None)
            start_date = form.cleaned_data.get('start_date', None)
            book = Book.objects.get(id=id_book)
            customer = Customer.objects.get(id=id_customer)
            new_return = Return(
                book=book
                start_date=start_date)
            txn=Loan_Txn(
                customer=customer,
                book=book,
                start_date=start_date
            )

            try
                with transaction.atomic():
                    book.update(status="ON_LOAN")
                    new_return.save(force_insert=True)
                    txn.save(force_insert=True)
            except IntegrityError:
                raise forms.ValidationError("Something occured. Please try again")

关于这个，我还遗漏了什么吗？我使用的是 Django 1.9 和 Python 3.4.3，数据库是 MySQL。

Answer 1

您正确地使用了 transaction.atomic()(包括将 try ... except 放在事务之外)但是您绝对不应该设置 自动提交 = 假。

作为documentation状态，当你想“禁用 Django 的事务管理”时，你将系统范围的设置设置为 False——但这显然不是你想要做的，因为你是使用 transaction.atomic()!更多来自 documentation :

If you do this, Django won’t enable autocommit, and won’t perform any commits. You’ll get the regular behavior of the underlying database library. This requires you to commit explicitly every transaction, even those started by Django or by third-party libraries. Thus, this is best used in situations where you want to run your own transaction-controlling middleware or do something really strange.

所以不要那样做。 Django 当然会为该原子 block 禁用自动提交并在 block 完成时重新启用它。