Cool, I think the approach you outlined briefly works, and I look forward to hopefully seeing it in the next release.
For now, I will just add the columns back to the AutocreatedGroup class. Again, thank you. I really appreciate your help. I'll make sure to make my emails in the future more explanatory according to your input. On Wednesday, August 15, 2012 12:22:59 PM UTC-4, Michael Bayer wrote: > > > On Aug 15, 2012, at 11:41 AM, Kuba Dolecki wrote: > > You responded! Woot. Thanks. Here's some additional info: > > 1. __tablename__ is generated automatically based on the class name. > Flask-SQLAlchemy does this for us. The __tablename__ for AutocreatedGroup > and TopicAutocreatedGroup model is both "autocreated_group". > > > <many questions here, removed once I read point #2> > > > 2. Sorry, I might have included too much code in my snippet. Group extends > Community through joined table inheritance (primary key with foreign key to > community). AutocreatedGroup extends Group in the same manner. The > relationship of interest is between AutocreatedGroup and > TopicAutocreatedGroup. TopicAutocreatedGroup does appear to inherit through > a single table. > > > OH. no, this wasn't *enough* code. I always need to know the full > expanse of classes and tables in play. I'll recreate the full mapping now > based on your descriptions here in order to reproduce. > > > 3. Yeah, I'm redefining polymorphic_on for Group since it depends on a > boolean switch. I'm doing the same for AutocreatedGroup since it depends on > the name of the class. > > AutocreatedGroup and TopicAutocreatedGroup do appear to have all of the > same columns of Group and Community. The AutocreatedGroup table does have > the topic_created_from_id column, but that same column doesn't appear in > the mapper. > > > there is logic added to declarative that detects columns applied to a > single table inheritance subclass, and moves them up to the superclass > table, mapping it only for the subclass. Due to the complex and deep chain > of mappings here, this logic is likely failing. let's create a test case > and see. (goes to do that).....OK yeah this isn't going to work right now > and would require a major architectural change to the expression system in > order to accommodate. The declarative system adds the new column to the > AutocreatedGroup.__table__ correctly. However, AutocreatedGroup's "mapped" > table is the join() of community->group->autocreated_group. The collection > of columns on this join() object is determined only once from the Table > objects given to it. Adding a new column to one of those Table objects > after the fact is not affecting that collection so the column isn't mapped. > > There's ways this might work but they are definitely destabilizing, I'l > try to see if I can put something into 0.8 for that - basically I'd make > derived selectables add an event listener to the selectable they're derived > from, so that new column additions can propagate. > > However, to make this work for now you'd need to declare > topic_created_from_id on the AutocreatedGroup class directly. A more > involved workaround would be to delay the production of mappings on the > hierarchy, though in 0.7 you need to do a slightly hacky approach for that > (it's what's described in > https://bitbucket.org/sqlalchemy/sqlalchemy/src/f47a971874b6/examples/declarative_reflection/declarative_reflection.py > ). > > > > Thanks, again. I'm definitely not a SQL Alchemy expert, so your help is > appreciated greatly. > > On Wednesday, August 15, 2012 11:21:41 AM UTC-4, Michael Bayer wrote: >> >> >> On Aug 15, 2012, at 10:45 AM, Kuba Dolecki wrote: >> >> Hi, >> >> We've used joined table inheritance up to this point, but performance >> issues are making us explore single table inheritance. I'm running into a >> problem with mapper configuration. Using SQLAlchemy 0.7.8, Flask-SQLAlchemy >> 0.16, and Flask 0.8. Here is the inheritance: >> >> >> there are many things that are confusing about this model. >> >> 1. I don't see any mention of __tablename__ anywhere. Where is the >> table defined ? >> >> 2. You say this is single table inheritance, but I see each subclass has >> it's own primary key column, with a foreign key column pointing back to the >> superclass "table" (which isn't present). This doesn't fit with single >> table inheritance at all. >> >> 3. There's a second re-definition of "polymorphic_on". This isn't >> necessarily a mistake, as it is supported that loading a specific >> sub-hierarchy may have a different system of determining polymorphic >> identity - usually this applies to concrete schemes. But with joined or >> single table inheritance it's extremely unusual, as the base table is what >> determines object identity in both of these cases. If you load a >> collection of "community" rows, the ORM needs to decide from that base >> table alone what the subclass should be. It won't see a >> sub-polymorphic-on unless the original query was against that subclass. >> >> >> class Community(BaseModel, db.Model): >> # Bar >> >> class Group(Community): >> ### >> Group utilized joined table inheritance to extend Community >> ### >> id = db.Column(db.Integer, db.ForeignKey('community.id'), >> primary_key=True, nullable=False) >> autocreated = db.Column(db.Boolean, nullable=False, default=False) >> >> @declared_attr >> def __mapper_args__(cls): >> name = cls._name() >> identity = { >> 'polymorphic_on': case([ >> (cls.autocreated == True, "autocreated_group"), >> (cls.autocreated == False, "group") >> ]), >> 'polymorphic_identity': name >> } >> return identity >> >> class AutocreatedGroup(Group): >> ### >> AutocreatedGroup extends Group through joined table inheritance >> ### >> id = db.Column(db.Integer, db.ForeignKey('group.id'), >> primary_key=True, \ >> nullable=False) >> >> @declared_attr >> def __mapper_args__(cls): >> name = cls._name() >> identity = { >> 'polymorphic_on': cls.autocreated_type, >> 'polymorphic_identity': name >> } >> return identity >> >> class TopicAutocreatedGroup(AutocreatedGroup): >> ### >> TopicAutocreatedGroup extends AutocreatedGroup through single >> table inheritance >> ### >> @declared_attr >> def __mapper_args__(cls): >> return {'polymorphic_identity': cls._name()} >> >> topic_created_from_id = db.Column( >> db.Integer, >> db.ForeignKey('topic.id'), >> nullable = True >> ) >> topic_created_from = db.relation( >> "Topic", >> primaryjoin="Topic.id == >> TopicAutocreatedGroup.topic_created_from_id", >> backref=db.backref("topic_groups", uselist=True), >> uselist=False, lazy='subquery' >> ) >> >> Here is the stacktrace: >> Traceback (most recent call last): >> File "/srv/.env/lib/python2.6/site-packages/flask/app.py", line 1518, >> in __call__ >> return self.wsgi_app(environ, start_response) >> File "/srv/.env/lib/python2.6/site-packages/flask/app.py", line 1506, >> in wsgi_app >> response = self.make_response(self.handle_exception(e)) >> File "/srv/.env/lib/python2.6/site-packages/flask/app.py", line 1504, >> in wsgi_app >> response = self.full_dispatch_request() >> File "/srv/.env/lib/python2.6/site-packages/flask/app.py", line 1264, >> in full_dispatch_request >> rv = self.handle_user_exception(e) >> File "/srv/.env/lib/python2.6/site-packages/flask/app.py", line 1260, >> in full_dispatch_request >> rv = self.preprocess_request() >> File "/srv/.env/lib/python2.6/site-packages/flask/app.py", line 1387, >> in preprocess_request >> rv = func() >> File "/srv/franklin-api/api/helpers/login_manager.py", line 53, in >> _load_user >> user = User.for_auth_token(token) >> File "/srv/franklin-api/api/models/user.py", line 584, in for_auth_token >> user_for_token = cls.query.filter(cls.auth_token == >> auth_token).first() >> File "/srv/.env/lib/python2.6/site-packages/flask_sqlalchemy.py", line >> 394, in __get__ >> mapper = orm.class_mapper(type) >> File "/srv/.env/lib/python2.6/site-packages/sqlalchemy/orm/util.py", >> line 660, in class_mapper >> mapperlib.configure_mappers() >> File "/srv/.env/lib/python2.6/site-packages/sqlalchemy/orm/mapper.py", >> line 2255, in configure_mappers >> raise e >> InvalidRequestError: One or more mappers failed to initialize - can't >> proceed with initialization of other mappers. Original exception was: >> Class <class 'api.models.autocreated_group.TopicAutocreatedGroup'> does not >> have a mapped column named 'topic_created_from_id' >> >> >> It appears the Columns inside classes that inherit through single table >> inheritance are not included in the mapper. Any idea of what may be going >> wrong? >> >> Thank you, >> Kuba >> >> P.S. What should __mapper_args__ look like for AutocreatedGroup? Should >> "topic_created_from_id" be automatically included in the >> "excluded_properties" value? Currently, it's empty if I print it out. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "sqlalchemy" group. >> To view this discussion on the web visit >> https://groups.google.com/d/msg/sqlalchemy/-/l3a-3tBjaf4J. >> To post to this group, send email to sqlal...@googlegroups.com. >> To unsubscribe from this group, send email to >> sqlalchemy+...@googlegroups.com. >> For more options, visit this group at >> http://groups.google.com/group/sqlalchemy?hl=en. >> >> >> > -- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To view this discussion on the web visit > https://groups.google.com/d/msg/sqlalchemy/-/iUiRCq6w7bcJ. > To post to this group, send email to sqlal...@googlegroups.com<javascript:> > . > To unsubscribe from this group, send email to > sqlalchemy+...@googlegroups.com <javascript:>. > For more options, visit this group at > http://groups.google.com/group/sqlalchemy?hl=en. > > > -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. 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