Question

我正在使用SQLAlchemy并尝试管理与“预订”具有多对一关系的“媒体”模型。在scoped_session.delete()事件中呼叫before_commit是否安全？

def before_commit(session):
    r""" Invokes the ``before_commit`` method on all items in the session.
    This allows the models to perform an update-action depending on their
    new data. """

    for item in session.deleted:
        if hasattr(item, 'before_commit'):
            item.before_commit(session, 'deleted')

    for item in session.dirty:
        if hasattr(item, 'before_commit'):
            item.before_commit(session, 'dirty')

    for item in session.new:
        if hasattr(item, 'before_commit'):
            item.before_commit(session, 'new')

event.listen(db.session.__class__, 'before_commit', before_commit)

class Booking(db.Model):

    # ...

    media = db.relationship(Media, backref='booking')

    def before_commit(self, session, status):
        r""" Validates the booking's data. If the booking is being deleted,
        all its media will be deleted with it. """

        if status == 'deleted':
            # Delete all the media that is associated with this booking.
            for media in self.media:
                session.delete(media)

Answer 1

使用session.execute（“delete ...”）或session.query（cls）.delete（）的mass delete（）应该没问题，它只是在当前连接上发出SQL。

就session.delete（obj）而言，看起来在最终的flush（）之前调用了before_commit（），所以在这种意义上你可以把它当作before_flush（）事件来对待它。尝试一下，你应该看到发出DELETE，如果是，那你就没事了。

SQLAlchemy是对before_commit安全删除吗？

1 个答案: