Question

This is my base class

class Product(Base):
    __tablename__ = 'PRODUCT'
    __table_args__ = {'quote':False}

    ...
    id = Column(Integer, name='id_prod', primary_key=True)
    type = Column(String(100),name='id_typ_prod')

    __mapper_args__ = {'polymorphic_on': type}

So, naturally we have a number of classes that extends from this Product, e.g. Phone and Cable, each of them maps to its own table.

class Phone (Product):
    __tablename__ = 'PHONE'
    ...

Now for some reasons now I want to create a ‘alias’ class, a class that does not have a corresponding table in database. Something like this:

class VapourWare(Product):
     ...

If I do

class VapourWare(Product):
    __tablename__ = 'PRODUCT'
    __mapper_args__ = {'polymorphic_identity':'VapourWare'}

It seems to work. But is it the right or recommended way? I am repeating __tablename__ = 'PRODUCT' here.

Answer 1

To some degree it depends on what you’re trying to achieve, but from your example it seems that what you’re trying to do is called Single-Table Inheritence in the SA Docs. The example listed on the linked page seems very much like your example, with Employee == Product and Manager == VapourWare (insert Dilbert joke here).