On Thu, Nov 19, 2009 at 14:42, lea <[email protected]> wrote: > Hi all, > i have an entity Question with a ManyToMany relationship answer_codes. > In an @before_insert or @after_insert, I'd like to add answer codes to > the answer_codes relationship. When I then flush or commit the > question is inserted into the database, the answer code relationship > entities however are not (the answer code entities already exist in > the database). Did I do something wrong or is this supposed to be like > that? > > class Question(Entity): > ... > answer_codes = ManyToMany('AnswerCode', > tablename='rel_question_to_answer_code', > onupdate='CASCADE', > ondelete='CASCADE') > > �...@before_insert > def add_answer_codes(self): > for answer_code in self.valid_answer_codes: > self.answer_codes.append(AnswerCode.get_by > (code=answer_code)) > > Cheers, > Lea
Two problems here: 1) if you add objects in a relation in an "event listener", it won't have any effect directly. The list of objects to flush to the database has already been computed and it's "too late" to do so at this point. Your changes will only be computed on the next flush. 2) you query using the ORM within the even listener, which will (in most cases) cause a flush to happen, which is a bad thing since you are already in the process of a flush (before_insert is a hook which is called by a flush). I suggest you use "after_insert" instead, and use the SQL layer to insert those records. It would produce a second query to the database, so that might not be optimal. Another option would be to use a session extension instead: before_flush (or any other). But then you'd have to use an isinstance call to check that it is a Question instance, and also check that it's actually a new instance, not an old one, that you are updating, kinda tedious... Another option would be to bring this to the SQLAlchemy list where you might receive other suggestions and you could potentially ask for a new feature to ease that use case. For a bit more details, see: http://www.sqlalchemy.org/docs/05/reference/orm/interfaces.html?highlight=mapperextension#sqlalchemy.orm.interfaces.MapperExtension.before_insert -- Gaëtan de Menten http://openhex.org -- You received this message because you are subscribed to the Google Groups "SQLElixir" group. To post to this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/sqlelixir?hl=.
