On 4/29/15 12:11 PM, st...@canary.md wrote:
Since my association object doesn't have extra columns, the row ('bob,
'apple') will be deleted. However, if there are extra columns, then
having it marked as "dirty" is desired.
Perhaps I would delay my recording of my audit rows until after
orphans are resolved. I am already using "after_flush", is there
another event I could use? Otherwise, I would need to detect an object
as an association object without extra columns and perform specific
logic to handle this. Is there a way to identify association objects?
there's not an event in between the time that the orphan thing is
calculated and the SQL is emitted. After flush is a candidate if you
can make that work.
The approach using the event is just to make an event listener for this
purpose and apply it to those classes that need it:
class MyParent(Base):
# ...
associations = relationship("MyAssociation", cascade="all,
delete-orphan")
@event.listens_for(MyParent.associations, "remove")
def on_remove(obj, child, initiator):
object_session(obj).delete(child)
class MyAssociation(Base):
# ...
Thanks!
On Tuesday, April 28, 2015 at 7:53:21 PM UTC-4, Michael Bayer wrote:
On 4/28/15 6:57 PM, st...@canary.md <javascript:> wrote:
Hi,
Background information: I am trying to implement functionality
similar to the history_meta.py example
(http://docs.sqlalchemy.org/en/rel_0_9/_modules/examples/versioned_history/history_meta.html
<http://docs.sqlalchemy.org/en/rel_0_9/_modules/examples/versioned_history/history_meta.html>).
I am listening for after_flush events and create an audit record
and am having problems with association objects. Here is an example:
class User(Auditable, self.Base, ComparableEntity):
__tablename__ = 'usertable'
id = Column(Integer, primary_key=True)
name = Column(String)
keywords = association_proxy('assocs', 'keyword')
class Keyword(Auditable, self.Base, ComparableEntity):
__tablename__ = 'keywordtable'
id = Column(Integer, primary_key=True)
word = Column(String)
class UserKeyword(Auditable, self.Base, ComparableEntity):
__tablename__ = 'userkeywordtable'
user_id = Column(Integer, ForeignKey("usertable.id
<http://usertable.id>"),
primary_key=True)
keyword_id = Column(Integer, ForeignKey("keywordtable.id
<http://keywordtable.id>"),
primary_key=True)
user = relationship(User,
backref=backref("assocs",
cascade="all, delete-orphan"))
keyword = relationship(Keyword)
def __init__(self, keyword=None, user=None):
self.user = user
self.keyword = keyword
apple = Keyword(word='apple')
pear = Keyword(word='pear')
bob = User(name='bob')
bob.keywords = [apple, pear]
sess.add(bob)
sess.commit()
bob.keywords.remove(apple) <====== this is when my question is
about
sess.commit()
When we remove the keyword, it marks the UserKeyword association
object is "dirty" instead of "deleted". Why is that? Since the
row is being removed, I would expect it to be marked as
"deleted", so that I could make an audit record indicating it was
deleted.
does the row actually get deleted? the calculation of "orphan"
isn't done until flush time, because theoretically you could be
associating the UserKeyword to another User.
it doesn't look like the versioned rows recipe has support for
this use case right now. You could force the up-front delete
using a "remove" attribute event on that collection.
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