[sqlalchemy] expunge cascade behavior change
Somewhere between 0.6.4 and 0.7.5, the expunge cascade behavior
changed. Can you help me understand what changed/point me to the
ticket? The attached script assertions succeed in 0.6.4 but the last
one fails in 0.7.5. It doesn't seem wrong, but I'm wondering what the
behavior was defined as previously and if that was considered a bug, etc.
Thanks,
Kent
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from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.orm.util import has_identity
engine = create_engine('sqlite:///', echo=True)
metadata = MetaData(engine)
Session = sessionmaker(bind=engine)
rocks_table = Table(rocks, metadata,
Column(id, Integer, primary_key=True),
)
bugs_table = Table(bugs, metadata,
Column(id, Integer, primary_key=True),
Column(rockid, Integer, ForeignKey('rocks.id'),),
)
class Rock(object):
def __repr__(self):
return 'Rock@%d: id=[%s] in session:[%s] has_identity[%s]' % (id(self), self.__dict__.get('id'), self in session, has_identity(self))
class Bug(object):
def __repr__(self):
return 'Bug@%d: id=[%s] rockid[%s] with rock[%s]' % (id(self), self.__dict__.get('id'), self.__dict__.get('rockid'), self.__dict__.get('rock','not set'))
mapper(Rock, rocks_table,
properties={'bugs': relationship(Bug,
cascade='all,delete-orphan',
backref=backref('rock',cascade='refresh-expire,expunge'))
})
mapper(Bug, bugs_table)
metadata.create_all()
session = Session()
# add a rock and bug
rock=Rock()
rock.id = 0
bug=Bug()
bug.id = 0
rock.bugs.append(bug)
session.add(rock)
session.commit()
# later... new session
session = Session()
rock = session.query(Rock).get(0)
rock.bugs.append(Bug())
assert rock in session
rock.bugs = []
assert rock in session
[sqlalchemy] Expunge
If I retrieve data strictly for reporting or other read-only use, e.g. the session will not be used to update data, should I expunge the objects returned by the query from the session? If I just let the session object go out of scope is that sufficient? Thanks, Mark -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] Expunge
On 2010-09-25 2:29 PM, Mark Erbaugh wrote: If I retrieve data strictly for reporting or other read-only use, e.g. the session will not be used to update data, should I expunge the objects returned by the query from the session? If I just let the session object go out of scope is that sufficient? If you're not modifying the objects, then you don't have to do anything at all. If you are modifying them, then as long as you don't call commit() on the session, the changes will be discarded when the session is deleted. (That's assuming you have autocommit==False). (Also, I think go out of scope is ambiguous in Python, where what really matters is whether there are other references to the session. Only when the last reference is removed is the session garbage-collected and the changes will discarded/rolled-back. Having a local variable referencing the session go out of scope does nothing if there are other non-local references to the same session. But you probably know all that. :) ) -- Peter Hansen -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
[sqlalchemy] expunge vs clear
I'm using an orm configuration with a sessionmaker().mapper doing the
mapping between my classes and my metadata.
The documentation says that doing a Session.clear() should do the
equivalent of a Session.expunge(inst) for all instances attached to
the session.
I have one instance attached to the session, and do a Session.clear();
but if I then re-query to get that instance, I get
InvalidRequestError: Could not update instance '[EMAIL PROTECTED]',
identity key (class 'cobalt.model.base.Job', ('localhost', 0),
None); a different instance with the same identity key already exists
in this session.
If I replace the Session.close() with a Session.expunge(inst), the
error goes away.
Any ideas?
~jon
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