[Sqlalchemy-tickets] Issue #3636: abstract class inheritors not behaving properly (zzzeek/sqlalchemy)

[Daniel K. <iss...@bi...>]

New issue 3636: abstract class inheritors not behaving properly
https://bitbucket.org/zzzeek/sqlalchemy/issues/3636/abstract-class-inheritors-not-behaving

Daniel Kassen:

Below is a snippet of code that defines a Parent class and a Child class which is abstract and used for inheritance. Classes that inherit from Child do not automatically populate if the entry exists in the database. By that, I mean the proper query is not performed to automatically pull that object out from the database even though it exists, causing duplicate entry errors when commit()'ing the session.

```
#!python

class Parent(Base):
    __tablename__ = 'parent'

    id = Column(Integer, primary_key=true)
    name = Column(String(100, collation='utf8_bin'),
                  nullable=False, unique=True)


class Child(Base):
        __abstract__ = True

        @classmethod
        def _classname(cls):
            return cls.__name__

        @delcared_attr
        def __tablename__(self):
            return self._classname().lower()
        
        @delcared_attr
        def id(self):
            return Column(Integer, ForeignKey(Parent.id), primary_key=True)

        @declared_attr
        def parent(self):
            return relationship(Parent)
```
Creating a factory that declares a class with the same attributes as are declared above in the Child class actually works, which is why this isn't very high priority, but it does make my code much less pythonic. Classes created from the factory below auto-populate as they should.
```
#!python

def create_child(name):
    class Child(Base):

        __tablename__ = name.lower()

        id = Column(Serial, ForeignKey(Parent.id), primary_key=True)

        parent = relationship(Parent)

    Child.__name__ = name
    return Child
```

Responsible: zzzeek