First, let me say that I'm using sqlalchemy version 0.5.8. We have a
large and complex application and changing to sa 0.6 is expensive, so
I would like, if possible, to find a solution for 0.5. I'm using
sqlalchemy since version 0.1.
Problem: objects are one moment inside a session an the other moment
are not.
Setup:
Session is in weak_identity_map=False mode:
maker = sessionmaker(autoflush=True, autocommit=False,
weak_identity_map=False,
extension=[ZopeTransactionExtension(), EpiSessionExtension()])
DBSession = scoped_session(maker)
All objects are immediately added to session:
campaign = Campaign(...)
DBSession.add(campaign)
Plus, the reference to object is kept locally.
Plus, the object is assigned to another relation property:
qitem = QItem(campaign=campaign, ...)
DBSession.add(qitem)
Now, the problem occurs at two different random points. Both time
the garbage collector is collecting the garbage before the problem
presents itself. This may have nothing to do with a problem.
Everything happens inside a single thread.
First case:
campaign = Campaign(...)
DBSession.add(campaign)
...
# called indirectly because of lots of queries
DBSession.flush()
print campaign.id # 206
# A: the (<Campaign>, 206) is inside the keys
print DBSession.identity_map.keys()
contact = DBSession.query(...).one()
# garbage is collected while this runs
# I can see it because of gc.set_debug(...)
# However, campaign is referenced locally and gc
# leaves it, but maybe some other internal SA object
# is collected.
# B: the (<Campaign>, 206) is no longer present
print DBSession.identity_map.keys()
Second case, very similar, but problem appears at a later point:
campaign = Campaign(...)
DBSession.add(campaign)
DBSession.flush()
print campaign.id # 207
contact = DBSession.query(...).one()
# Also, assign campaign to relational property of `qitem`
qitem = QItem(campaign=campaign, ...)
DBSession.add(qitem)
# The (<Campaign>, 207) is inside the keys
print DBSession.identity_map.keys()
DBSession.flush() # called via commit by web controller
# DB raises exception CONTACT_ID cannot be NULL
The exception is raised because the `campaign` object
again got expunged from session for some reason, even
though the `qitem` itself holds a reference to it.
Sometimes everything finishes just fine.
I'm loosing sleep over this problem.
Regards,
Tvrtko
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