On Jun 4, 2013, at 1:55 AM, Amir Elaguizy <aelag...@gmail.com> wrote:
> Hi there, > > I have a tree that looks like this, reflected via polymorphic inheritance: what do we mean "reflected" here, are you reflecting tables from the database, that is, http://docs.sqlalchemy.org/en/rel_0_8/core/schema.html#metadata-reflection ? > > That works great, like: > > > class BaseModel(db.Model): # Table A in diagram > __tablename__ = "entities" > > id = db.Column(db.BigInteger, primary_key=True, nullable=False, > server_default=func.nextval('guid_seq')) > type_id = db.Column(db.SmallInteger, db.ForeignKey(EntityTypesModel.id)) > > __mapper_args__ = { > 'polymorphic_identity':'entity', > 'polymorphic_on':type_id, > 'with_polymorphic':'*' > } this is why I question the word "reflected" because I don't see you using reflection there. > > class BrandModel(BaseModel): # Table B, C, D in diagram > __tablename__ = 'brands' > > id = db.Column(db.BigInteger, db.ForeignKey(StufffModel.id), > primary_key=True, nullable=False) > name = db.Column(db.String, nullable=False) > > __mapper_args__ = { > 'polymorphic_identity':ET_BRAND, > } Im confused by this as well - are you saying that you map the same class to B, C, and D rows? That would be unusual. It wouldn't work at all on the persistence side as SQLAlchemy could not know which of B, C, or D you wish for a particular BrandModel to be persisted towards. > > > The problem is I need to reflect something more like this: > > A > / | \ > B C D > / \ > E F > > Where D is not only a polymorphic child of A but also the polymorphic parents > of E & F. > > It seems like I have to choose, D can either be a polymorphic child or it can > be a parent - it can't be both. > > Do I have any options here? SQLAlchemy can represent inheritance hierarchies of any depth. However, because you are assigning a single subclass to all of B, C, and D that might be why there's an issue here, you'd need to assign a distinct subclass of BaseModel to at least "D", and then another subclass of D_Model to handle E and F. Preferably, you'd produce distinct classes for all six tables. -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
