Question

我有以下代码片段对Customer表进行操作：

with session.begin(subtransactions=True):
    db_obj = Customer(...)

result = io_processing() # may cause greenlet switching

# I do not want to make it inside the transaction above,
# Because some legacy I/O related code which will causes greenlet switching
if result:
    self.read_write_db(session, db_obj)

在read_write_db函数中：

with session.begin(subtransactions=True):
    # do some work on db_obj passed from outside

将事务外的'db_obj'传递给另一个函数是否安全？

或者我必须在read_write_db中再次查询db_obj并更新它？

Answer 1

是的，这是可能的，但您必须通过在db_obj的会话中合并read_write_db来获取新实例。

with session.begin(subtransactions=True):
    merged_db_obj = session.merge(db_obj)
    # work with merged_db_obj ...

有关所有详细信息，请参阅http://docs.sqlalchemy.org/en/rel_0_9/orm/session.html#merging。合并可能很棘手。

访问SQLAlchemy数据库会话外的表对象

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