SQLAlchemy before_update called instead after_delete

Question

Can anybody tell what I'm doing wrong

I have method with which register event (before_update, after_delete, before_insert) https://github.com/ITCase/sqlalchemy_mptt/blob/b0efead7a8ee5acc063b68ee3bfc756af4689d6e/sqlalchemy_mptt/mixins.py#L69

@classmethod
def register_tree(cls):
    event.listen(cls, "before_insert", cls.mptt_before_insert)
    event.listen(cls, "after_delete", cls.mptt_after_delete)
    event.listen(cls, "before_update", cls.mptt_before_update)

When I registered event and try to delete row (https://github.com/ITCase/sqlalchemy_mptt/blob/b0efead7a8ee5acc063b68ee3bfc756af4689d6e/sqlalchemy_mptt/tests.py#L104).

class Tree(Base, BaseNestedSets):
    __tablename__ = "tree"

    id = Column(Integer, primary_key=True)

Tree.register_tree()

def test_delete_node(self):
    node = self.session.query(Tree).filter(Tree.id == 4).one()
    self.session.delete(node)
    # id lft rgt lvl parent tree
    self.assertEqual([(1, 1, 16, 1, None, 1),
                      (2, 2, 5, 2, 1, 1),
                      (3, 3, 4, 3, 2, 1),
                      (7, 6, 15, 2, 1, 1),
                      (8, 7, 10, 3, 7, 1),
                      (9, 8, 9, 4, 8, 1),
                      (10, 11, 14, 3, 7, 1),
                      (11, 12, 13, 4, 10, 1)], self.result.all())

Called before_update method instead after_delete. But if I comment before_update event (https://github.com/ITCase/sqlalchemy_mptt/blob/b0efead7a8ee5acc063b68ee3bfc756af4689d6e/sqlalchemy_mptt/mixins.py#L72) it's work fine.

@classmethod
def register_tree(cls):
    event.listen(cls, "before_insert", cls.mptt_before_insert)
    event.listen(cls, "after_delete", cls.mptt_after_delete)
    # event.listen(cls, "before_update", cls.mptt_before_update) <-- IF comment this, called after_delete method. It's OK.

Build status https://travis-ci.org/ITCase/sqlalchemy_mptt/builds/23428309

What's wrong?

Answer 1

Solve it there https://groups.google.com/forum/#!msg/sqlalchemy/gdwuMjNfrPc/v2ChQjGjWwoJ

It turns out that when remove node with children, sqlalchemy by defaults first update children (set parent_id=None) and then delete node. When I set cascade="all,delete" it's delete node one by one (w/o update).