Python Sqlalchemy：在nested_transaction 会话中回滚会撤消外部事务中的提交

如何解决Python Sqlalchemy：在nested_transaction 会话中回滚会撤消外部事务中的提交

我正在使用 unittest 测试我的程序，但发生了一些奇怪的事情。基本上，当我使用 session.rollback() 并且此会话附加到嵌套事务时，插入到外部事务中的对象就会消失。这是与数据库的集成测试，因此我以这种方式构建了测试：

1. 方法 setUpClass（在这个测试用例的所有测试中只调用一次）：创建与数据库的初始连接并用数据填充它。
2. method setUp（每次执行此测试用例的测试时调用）：创建一个嵌套事务并创建一个会话工厂，该会话工厂返回附加到此嵌套事务的新会话（此事务在结束时回滚）在tearDown方法中测试）。

好吧，当我回滚在第二步中创建的会话时，在第一步中填充的数据消失了（这不应该发生，对吧？NESTED 事务中的回滚不应该删除已经提交的外部事务中的内容).

代码：

class Person(Base):
    __tablename__ = 'people'

    id = Column(Integer,primary_key=True,autoincrement=True)
    name = Column(String(50),nullable=False)
    email = Column(String(50),nullable=False)


class HandlerTest:
    def __init__(self,session_maker):
        self.session_maker = session_maker

    def get_by_email(self,email: str):
        session: Session = self.session_maker()
        try:
            person = session.query(Person).filter_by(email=email).first()
        finally:
            session.rollback()
            session.close()

        return person


class MyTestCase(unittest.TestCase):
    @classmethod
    def setUpClass(cls) -> None:
        cls.engine = create_engine('CONN_STRING')
        cls.conn = cls.engine.connect()
        cls.outer_trans = cls.conn.begin()
        cls.base_session = Session(bind=cls.conn)

        cls.people = [
            Person(name='Jorg',email='[e-mail]'),Person(name='Peter',email='[e-mail]'),Person(name='Ivone',email='[e-mail]')
        ]

        for p in cls.people:
            cls.base_session.add(p)

        cls.base_session.commit()

    @classmethod
    def tearDownClass(cls) -> None:
        cls.base_session.close()
        cls.outer_trans.rollback()
        cls.conn.close()
        cls.engine.dispose()

    def setUp(self) -> None:
        def make_session():
            return Session(bind=self.conn)

        self.trans = self.conn.begin_nested()
        self.db_maker = Mock()
        self.db_maker.side_effect = make_session
        self.session = self.db_maker()

        self.handler = HandlerTest(session_maker=self.db_maker)

    def tearDown(self) -> None:
        self.session.close()
        self.trans.rollback()

    def test_something(self):
        print(f'Initial count: {self.session.query(Person).count()}')

        for p in self.people:
            print('Calling handler...')
            ret = self.handler.get_by_email(p.email)

            print(f'Count: {self.session.query(Person).count()}')


if __name__ == '__main__':
    unittest.main()

当我运行测试时，这是控制台的返回：

Initial count: 3
Calling handler...
Count: 3
Calling handler...
Count: 0
Calling handler...

Error
Traceback (most recent call last):
  File "C:\Users\User\AppData\Local\Programs\Python\Python39\Lib\unittest\case.py",line 59,in testPartExecutor
    yield
  File "C:\Users\User\AppData\Local\Programs\Python\Python39\Lib\unittest\case.py",line 593,in run
    self._callTestMethod(testMethod)
  File "C:\Users\User\AppData\Local\Programs\Python\Python39\Lib\unittest\case.py",line 550,in _callTestMethod
    method()
  File "D:\Program\tests_src\test_handler\wtf\test_a.py",line 79,in test_something
    ret = self.handler.get_by_email(p.email)
  File "C:\Users\User\AppData\Local\Programs\Python\Python39\lib\site-packages\sqlalchemy\orm\attributes.py",line 287,in __get__
    return self.impl.get(instance_state(instance),dict_)
  File "C:\Users\User\AppData\Local\Programs\Python\Python39\lib\site-packages\sqlalchemy\orm\attributes.py",line 718,in get
    value = state._load_expired(state,passive)
  File "C:\Users\User\AppData\Local\Programs\Python\Python39\lib\site-packages\sqlalchemy\orm\state.py",line 652,in _load_expired
    self.manager.deferred_scalar_loader(self,toload)
  File "C:\Users\User\AppData\Local\Programs\Python\Python39\lib\site-packages\sqlalchemy\orm\loading.py",line 1016,in load_scalar_attributes
    raise orm_exc.ObjectDeletedError(state)
sqlalchemy.orm.exc.ObjectDeletedError: Instance '<Person at 0x2223a1e4bb0>' has been deleted,or its row is otherwise not present.

当我删除 get_by_email 方法中的 session.rollback() 行时，没有删除任何内容并且测试运行良好，没有任何问题。 SQLAlchemy 版本：1.3.20