The inheritance mechanics don't support multiple inheritance from the POV of multiple mapped classes as the base for another mapped class. Single table inheritance would be the easiest case to work at some point, but there's lots of mechanics in place right now that assume a linear path from subclass to superclass.
If you don't actually need instances of EvidenceString, EvidenceAmount, and EvidenceQuantity to exist in the database distinctly (that is, you'd never actually have any rows with "string", "amount", or "quantity" present in the DB as the discriminator), you'd define these as unmapped mixins, which is very well supported (see http://docs.sqlalchemy.org/en/rel_0_8/orm/extensions/declarative.html#mixin-and-custom-base-classes) . It seems here like that's what you're really looking for. On Jan 14, 2013, at 1:09 PM, Ethan Fremen wrote: > I have a pretty simple case. A base class with three sub-classes, and then a > final class that inherits from the three derived classes. When persisting, > sqlalchemy only sets the properties of the parent class and the first child > class. > > In all other respects the sub-class is behaving properly; it has the correct > attributes, etc. > > So, if EvidenceLineItem inherits from EvidenceString first, only the string > property (and the properties in Evidence) will update; if I change the first > inherited class to EvidenceAmount, amount will be persisted, but the rest not. > > I'll try declared_attr, but I'm pretty sure that this behaviour isn't what is > intended. > > ~ethan > > class Evidence(Base): > __tablename__ = "evidence" > discriminator = Column(DBEnum(ProofItemClassType), nullable=False) > __mapper_args__ = { 'polymorphic_on': discriminator, > 'polymorphic_identity': ProofItemClassType.generic } > > class EvidenceString(Evidence): > __mapper_args__ = { 'polymorphic_identity': ProofItemClassType.string } > string = Column(String(length=255), index=True) > > class EvidenceAmount(Evidence): > __mapper_args__ = { 'polymorphic_identity': ProofItemClassType.amount } > amount = Column(Numeric(precision=7, scale=2), index=True) > > class EvidenceQuantity(Evidence): > __mapper_args__ = { 'polymorphic_identity': ProofItemClassType.quantity } > quantity = Column(Integer) > > class EvidenceLineItem(EvidenceString, EvidenceAmount, EvidenceQuantity): > __mapper_args__ = { 'polymorphic_identity': ProofItemClassType.line_item } > > -- > 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/-/5hEAmVfC-EYJ. > To post to this group, send email to sqlalchemy@googlegroups.com. > To unsubscribe from this group, send email to > sqlalchemy+unsubscr...@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 post to this group, send email to sqlalchemy@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
