you need to specify primaryjoin and secondary join when you do self ref using
m2m. there's an example at the end of
http://www.sqlalchemy.org/docs/orm/relationships.html#specifying-alternate-join-conditions-to-relationship
, as well as some variants of that syntax which declarative introduces.
On Sep 30, 2010, at 3:15 PM, Julien Iguchi-Cartigny wrote:
> Hi,
>
> I've two classes CourseSet and CanonicalCourse (with the same parent)
> which need to be connected in a many-to-many relationship. But these
> classes are mapped on the same table, thus definition of the
> association table seems redondant:
>
> assoc_course_set_canonical_table = Table(
> 'CM_COURSE_SET_CANON_ASSOC_T', Base.metadata,
> Column('CANON_COURSE', Integer,
> ForeignKey('CM_MEMBER_CONTAINER_T.MEMBER_CONTAINER_ID')),
> Column('COURSE_SET', Integer,
> ForeignKey('CM_MEMBER_CONTAINER_T.MEMBER_CONTAINER_ID'))
> )
>
> But i can't define the relationship between. I've the error:
>
> Could not determine join condition between parent/child tables on
> relationship CourseSet.canonicalCourses. Specify a 'primaryjoin'
> expression. If 'secondary' is present, 'secondaryjoin' is needed as
> well.
>
> I must have miss something: i've tried several possibilities with
> primaryjoin and secondaryjoin but nothing work. Is it because i'm
> refering at the same foreign key in the associative table ?
>
> Thank you.
>
> Julien.
>
> PS: The code for my two classes ('#' comments the two lines with the problem)
>
> class CourseSet(AbstractContainer):
> parent_id = Column('PARENT_COURSE_SET', Integer,
> ForeignKey('CM_MEMBER_CONTAINER_T.ENTERPRISE_ID'))
> children = relationship("CourseSet", backref=backref('parent',
> remote_side=AbstractContainer.eid))
> # canonicalCourses = relationship("CanonicalCourse",
> # secondary="assoc_course_set_canonical_table")
>
> @classproperty
> def __mapper_args__(self):
> args = dict()
> args.update(AbstractContainer.__mapper_args__)
> args.update({'polymorphic_identity':
> 'org.sakaiproject.coursemanagement.impl.CourseSetCmImpl'})
> return args
>
> class CanonicalCourse(AbstractContainer):
>
> @classproperty
> def __mapper_args__(self):
> args = dict()
> args.update(AbstractContainer.__mapper_args__)
> args.update({'polymorphic_identity':
> 'org.sakaiproject.coursemanagement.impl.CanonicalCourseCmImpl'})
> return args
>
> PS: the parents of these classes:
>
> class AbstractPersistent(object):
> version = Column('VERSION', Integer)
> last_modified_by = Column('LAST_MODIFIED_BY', String(255))
> last_modified_date = Column('LAST_MODIFIED_DATE', Date)
> created_by = Column('CREATED_BY', String(255))
> created_date = Column('CREATED_DATE', Date)
>
> class AbstractNamed(AbstractPersistent):
> eid = Column('ENTERPRISE_ID', String(255))
> title = Column('TITLE', String(255))
> description = Column('DESCRIPTION', String(255))
>
> class AbstractContainer(Base,AbstractNamed):
> __tablename__ = 'CM_MEMBER_CONTAINER_T'
> id = Column('MEMBER_CONTAINER_ID',Integer,primary_key=True)
> discriminator = Column('CLASS_DISCR', String(100))
> __mapper_args__ = {'polymorphic_on': discriminator }
>
>
>
> --
> "Trouble-a-cat limited"
>
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