Hello,
Thank you for your answer, but unless I miss something in your answer my
problem has to do with polymorphic inheritance, it's not about relationship
between 2 models. By inheritance "updated_at" is an attribute of any Child
instance ( Child().updated_at exists).
I realize I didn't explained the example I joined:
(I also realize that Parent.__tablename__ is named 'entity', don't be
confused)
class definitions:
class Parent(Base):
__tablename__ = 'entity'
__mapper_args__ = {'polymorphic_on': 'entity_type',
'with_polymorphic': '*',
}
entity_type = Column('entity_type', String(1000), nullable=True)
id = Column('id', Integer(), primary_key=True)
name = Column('name', String(1000), default=u'')
updated_at = Column(sa.DateTime,
default=datetime.utcnow,
onupdate=datetime.utcnow)
class Child(Parent):
__tablename__ = 'child'
__mapper_args__ = {'polymorphic_identity': 'Child'}
id = Column(Integer,
ForeignKey('entity.id', name='fk_inherited_entity_id'),
primary_key=True)
text = Column('text', String(1000), default=u'')
When run() is executed:
obj = Child()
session.add(obj)
session.commit()
SQL emitted:
INSERT INTO entity (entity_type, name, updated_at) VALUES (?, ?, ?)
('Child', u'', '2013-11-08 10:27:18.886677')
INSERT INTO child (id, text) VALUES (?, ?)
(1, u'')
COMMIT
I change only one of Child's attributes:
obj.text = 'some text'
session.commit()
SQL:
UPDATE child SET text=? WHERE child.id = ?
('some text', 1)
COMMIT
-> updated_at on table entity is not changed, so obj.updated_at is left
untouched: don't want that.
But if I also change "name" (defined on Parent)
obj.name = u'test'
obj.text = 'some text'
session.commit()
SQL:
UPDATE entity SET name=?, updated_at=? WHERE entity.id = ?
(u'test', '2013-11-08 10:27:18.891200', 1)
UPDATE child SET text=? WHERE child.id = ?
('some text', 1)
COMMIT
obj.updated_at is changed.
Le vendredi 8 novembre 2013 12:09:13 UTC+1, Richard Gerd Kuesters a écrit :
>
> I think the code is correct and is behaving correctly also -- since you
> update just the child, the parent isn't touched (it already has data and
> was not changed in this session).
>
> What you could do is add an update event to your Child object:
>
>
> *def update_child(mapper, connection, target):*
> * # target is your child updated*
> * target.parent.updated_at = datetime.datetime.now() # assuming you
> have mapped parent as a backref object or something*
> * object_session(target).commit()*
>
> *event.listen(Child, 'after_update', update_child)*
>
>
> If you want the same after an insert or delete, you should declare other
> events[1] as well. I think there might be other ways to do that, but I
> usually use events for its flexibility.
>
> You can also use before_update to use the same session.commit()
>
> [1] http://docs.sqlalchemy.org/en/rel_0_8/orm/events.html
>
> Best regards,
> Richard.
>
> On 11/08/2013 08:38 AM, Bertrand Mathieu wrote:
>
> Hi,
>
> I have a set up class inheritance using joined table inheritance. I'm
> using sqlalchemy 0.8.2.
>
> The Parent class has a DateTime attribute "updated_at", with
> onupdate=datetime.utcnow.
>
> If I update only one of the Child's attributes, only "child" table is
> updated, parent.updated_at is not changed. If I change one of the Parent's
> attributes, then updated_at is updated as expected.
>
> Here's my questions:
> 1) Am I missing something in my setup? is it normal or is it a bug?
> 2) If this is normal, what is the right way to tell session that
> "parent.updated_at" should be modified too?
>
> Regards,
> --
> Bertrand
>
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