I am using python 3.3 and sqlalchemy 0.8.2
I am trying to define a self-referential many-to-many relationship for a
class where the primary key is provided by a mixin. Defining the primary
directly in the class works. Using the mixin does not.
I would be grateful for any suggestions or pointers to relevant
documentation.
Below is an example showing my problem. As given the example works.
Uncommenting the line "#id = ..." in 'Base' and commenting out the
corresponding line in 'A' breaks the example. Is there any way to define
the primary key in Base and getting the 'requires' relation to work?
-----------------------------------
from sqlalchemy import Column, Integer, String, DateTime, Table,
ForeignKey,create_engine
from sqlalchemy.ext.declarative import declarative_base,declared_attr
from sqlalchemy.orm import sessionmaker, relationship, backref
class Base(object):
#id = Column(Integer, primary_key=True)
pass
Base = declarative_base(cls=Base)
association_table = Table('association',
Base.metadata,
Column('prerequisite', Integer,
ForeignKey('a.id')),
Column('dependency', Integer, ForeignKey('a.id')))
class A(Base):
__tablename__ = "a"
id = Column(Integer, primary_key=True)
requires = relationship("A",
secondary = association_table,
primaryjoin=(id==association_table.c.prerequisite),
secondaryjoin=(id==association_table.c.dependency),
backref = backref("required_by"))
if __name__ == "__main__":
engine = create_engine('sqlite:///:memory:', echo=False)
Session = sessionmaker(bind=engine)
session = Session()
Base.metadata.create_all(engine)
T=A()
U=A()
session.add(T)
session.add(U)
T.requires.append(U)
session.commit()
print("T",T.id,T.requires,T.required_by)
print("U",U.id,U.requires,U.required_by)
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