Django - 回滚保存与交易原子

Question

我想创建一个视图，我保存一个对象，但我想撤消，如果引发一些异常保存。这是我试过的：

class MyView(View): 

    @transation.atomic 
    def post(self, request, *args, **kwargs): 
     try: 
      some_object = SomeModel(...) 
      some_object.save() 

      if something: 
       raise exception.NotAcceptable() 
       # When the workflow comes into this condition, I think the previous save should be undome 
       # Whant am I missing? 

     except exception.NotAcceptable, e: 
      # do something 

我在做什么错？即使在引发异常时some_object仍然在DataBase中。

Answer 1

Atomicity Documentation

总之，@transaction.atomic将在数据库上执行事务，如果您的视图产生没有错误的响应。因为你自己捕捉异常，所以Django显示你的视图执行得很好。

如果赶上例外，你需要自己处理：Controlling Transactions

如果你需要产生故障的情况下适当的JSON响应：

from django.db import SomeError, transaction 

def viewfunc(request): 
    do_something() 

    try: 
     with transaction.atomic(): 
      thing_that_might_fail() 
    except SomeError: 
     handle_exception() 

    render_response() 

Answer 2

但是，如果一个例外饰有transaction.atomic功能情况，那么你不要有什么关系，它会rollback automatically to the savepoint created by the decorator before running the your function，为documented：

原子允许我们创建一个块在其中保证数据库的原子性的代码。如果代码块成功完成，则更改将提交给数据库。如果有异常，则更改将回滚。

如果异常是在钓到除块，那么就应该再上调原子捕获它，做回退，即：

try: 
     some_object = SomeModel(...) 
     some_object.save() 

     if something: 
      raise exception.NotAcceptable() 
      # When the workflow comes into this condition, I think the previous save should be undome 
      # Whant am I missing? 

    except exception.NotAcceptable, e: 
     # do something 
     raise # re-raise the exception to make transaction.atomic rollback 

另外，如果你想要更多的控制，您可以手动回滚到previously set savepoint，即：

class MyView(View): 
    def post(self, request, *args, **kwargs): 
     sid = transaction.savepoint() 
     some_object = SomeModel(...) 
     some_object.save() 

     if something: 
      transaction.savepoint_rollback(sid) 
     else: 
      try: 
       # In worst case scenario, this might fail too 
       transaction.savepoint_commit(sid) 
      except IntegrityError: 
       transaction.savepoint_rollback(sid)