Hi everybody.
I'm stuck in something bad:
I use a relation with a arbitrary foreign key + backref (the reason is
that I use single table inheritance, and the relation happen only on
one of the subclasses, so I can't set the foreign key on the
table...). But I get quickly a circular dependency!
I don't really get why, so I wrote a piece of code to reproduce it and
post it here!
I hope someone got an explanation/solution! :)
Cheers!
ps: using the latest revision.
pps : I put the relation on the child side, but the same happens when
on the parent side.
from zope.sqlalchemy import ZopeTransactionExtension
from sqlalchemy.orm import scoped_session, sessionmaker, eagerload
from sqlalchemy import MetaData
from sqlalchemy.orm.interfaces import SessionExtension
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Table, Column, types
from sqlalchemy import ForeignKey, UniqueConstraint
from sqlalchemy.orm import relation, backref, synonym
from sqlalchemy import select, func
maker = sessionmaker(autoflush=True, autocommit=False,
extension=[ZopeTransactionExtension()])
DBSession = scoped_session(maker)
DeclarativeBase = declarative_base()
class Parent(DeclarativeBase):
__tablename__ = 'parent'
id = Column('id', types.Integer, primary_key=True,
nullable=False)
class Child(DeclarativeBase):
__tablename__ = 'child'
id = Column('id', types.Integer, primary_key=True,
nullable=False)
id_parent = Column('id_parent', types.Integer,
nullable=True)
parent = relation(Parent,
primaryjoin=id_parent==Parent.id,
foreign_keys=[Parent.id],
backref=backref('children',
foreign_keys=[id_parent],
cascade='all, delete-orphan',
passive_deletes=False))
p = Parent()
c = Child()
p.children.append(c)
DBSession.add(p)
DBSession.flush()
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