How to define two relationships to the same table in SQLAlchemy

Question

I’ve looked all over the SQLAlchemy tutorial and other similar questions but I seem to be struggling to get this join to work:

The scenario: I have

Answer 1

As of version 0.8, SQLAlchemy can resolve the ambiguous join using only the foreign_keys keyword parameter to relationship.

publish_user = relationship(User, foreign_keys=[publishing_user_id],
                                  backref=backref('pages', order_by=id))
edit_user = relationship(User, foreign_keys=[last_edit_user_id])

Documentation at http://docs.sqlalchemy.org/en/rel_0_9/orm/join_conditions.html#handling-multiple-join-paths

Answer 2

I think you almost got it right; only instead of Model names you should use Table names when defining primaryjoin. So instead of

# Define relationships
publish_user = relationship('User', backref = backref('pages', order_by = id), 
    primaryjoin = "Page.publishing_user_id == User.id")
edit_user = relationship('User', 
    primaryjoin = "Page.last_edit_user_id == User.id")

use:

# Define relationships
publish_user = relationship('User', backref = backref('pages', order_by = id), 
    primaryjoin = "pages.publishing_user_id == users.id")
edit_user = relationship('User', 
    primaryjoin = "pages.last_edit_user_id == users.id")

Answer 3

Try foreign_keys option:

publish_user = relationship(User, foreign_keys=publishing_user_id,
                                  primaryjoin=publishing_user_id == User.id,
                                  backref=backref('pages', order_by=id))
edit_user = relationship(User, foreign_keys=last_edit_user_id,
                               primaryjoin=last_edit_user_id == User.id)