Thanks for the swift reply. Eventually I solved it, by the hint in
your answer about the relationshop referring to no column. Replacing
parent_id = Column(Integer, ForeignKey('content.id'))
in the base class to
parent_id = Column(Integer, ForeignKey(id))
made the trick. It is however strange that the latter worked fine for
almost a year until I added a the 2nd FK in the derived classes
On 8 feb, 16:44, Michael Bayer <mike...@zzzcomputing.com> wrote:
> On Feb 8, 2012, at 9:39 AM, cropr wrote:
>
>
>
>
>
>
>
>
>
> > I aam having an issue defining a 2nd foreign key constraint on 2
> > derived classes of a base class that uses a self referential join.
>
> > Base class:ContentBase
>
> > class ContentBase(Base):
> > __tablename__ = 'content'
> > __mapper_args__ = {'polymorphic_on': ctype,
> > 'polymorphic_identity':'contentbase'}
> > id = Column(types.Integer, primary_key=True, autoincrement=True)
> > children = relationship("ContentBase", backref=backref('parent',
> > remote_side=id))
> > ....
>
> > Derived class CdRoot
>
> > class CdRoot(ContentBase):
> > __tablename__ = 'cdroot'
> > __mapper_args__ = {'polymorphic_identity' : 'cdroot'}
> > contentType = 'CdRoot'
> > id = Column(types.Integer, ForeignKey(ContentBase.id),
> > primary_key=True)
> > clubs = relationship('CdClub', primaryjoin="cdroot.id ==
> > cdclub.cdroot_id")
> > ...
>
> > Derived class CdClub
>
> > class CdClub(ContentBase):
> > __tablename__ = 'cdclub'
> > __mapper_args__ = {'polymorphic_identity' : 'cdclub'}
> > id = Column(types.Integer, ForeignKey(ContentBase.id),
> > primary_key=True)
> > cdroot_id = Column(types.Integer, ForeignKey(CdRoot.id))
> > ...
>
> > The 2nd join between CdRoot and CdClub fails with the message : Can't
> > determine join between content and
> > cdclub, tables have more than one FK constraint.
>
> > Apparently the primaryjoin condition is not sufficient to get rid of
> > the error. Any clue how to solve this
>
> Assuming this is paraphrasing since "cdroot.id==cdclub.cdroot_id" doesn't
> have the correct casing, also there's a relationship on ContentBase that
> doesn't appear to refer to any column but I assume that's under your "...".
>
> Filling in the blanks with reasonable guesses it works fine:
>
> from sqlalchemy import *
> from sqlalchemy.orm import *
> from sqlalchemy.ext.declarative import declarative_base
> from sqlalchemy.ext.associationproxy import association_proxy
>
> Base= declarative_base()
>
> class ContentBase(Base):
> __tablename__ = 'content'
> id = Column(Integer, primary_key=True, autoincrement=True)
> ctype = Column(String)
> parent_id = Column(Integer, ForeignKey('content.id'))
> children = relationship("ContentBase",
> backref=backref('parent',remote_side=id))
> __mapper_args__ = {'polymorphic_on':
> ctype,'polymorphic_identity':'contentbase'}
>
> class CdRoot(ContentBase):
> __tablename__ = 'cdroot'
> __mapper_args__ = {'polymorphic_identity' : 'cdroot'}
> contentType = 'CdRoot'
> id = Column(Integer, ForeignKey(ContentBase.id),primary_key=True)
> clubs = relationship('CdClub', primaryjoin="CdRoot.id ==CdClub.cdroot_id")
>
> class CdClub(ContentBase):
> __tablename__ = 'cdclub'
> __mapper_args__ = {'polymorphic_identity' : 'cdclub'}
> id = Column(Integer, ForeignKey(ContentBase.id),primary_key=True)
> cdroot_id = Column(Integer, ForeignKey(CdRoot.id))
>
> configure_mappers()
>
> if you still have problems, please provide a fully working example, thanks !
>
>
>
>
>
>
>
>
>
> > Ruben
>
> > --
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