On Oct 16, 2007, at 1:30 PM, [EMAIL PROTECTED] wrote:
> > Hi everybody! > > I've got a schema with a combined 1:n:1 + m:n relation. > In detail, I have the entities "user" and "event" and the relation > "participation". > That leads to 1:n user->participation, n:1 participation->event, and > m:n user->event: > > [user] 1 -- * [participation] * -- 1 [event] > * \_________________________________/ * > > Now the (assumed) bug is that the participation mapping only works > correctly after saving, flushing, clearing and retrieving the objects > (output only included where relevant): > > u = User(); u.name = "test user" > e = Event(); e.title = "test event" > u.events.append(e) > u.participations > [] #empty! > e.participations > [] #empty! > > session.save(u); session.save(e); session.flush(); session.clear() > u = session.query(User).get(1) > e = session.query(Event).get(1) > [<__main__.Participation object at 0x01035F50>] # not empty! > e.participations > [<__main__.Participation object at 0x01035F50>] # not empty! > > I think that the results should be identical before and after save/ > flush/clear/query. > Is this assumption wrong? > Am I really supposed to save/flush/clear/query my objects to get the > correct mappings? > Or is this a bug? the issue is you are using the participation_table as both a mapped table as well as an association table, which is not recommended; SA performs mapping operations with the table in two totally different ways which are not really compatible with each other (i.e., removing an Event from a User can leave existing Participation objects in your session in an invalid state). the advised pattern here is the "association object" pattern described in the docs: http:// www.sqlalchemy.org/docs/04/ mappers.html#advdatamapping_relation_patterns_association --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~----------~----~----~----~------~----~------~--~---
