SQLAlchemy circular one-to-one relationship

I am trying to make a circular one-to-one relationship (not sure what the correct term is) with SQLAlchemy that looks the following:

class Parent(Base):     __tablename__ = 'parents'     id = db.Column(Integer, primary_key=True)     child_id = db.Column(db.Integer,db.ForeignKey("children.id", use_alter=True))     child = db.relationship("Child",                         uselist=False,                         foreign_keys=[child_id],                         post_update=True)  class Child(Base):     __tablename__ = 'children'     id = db.Column(db.Integer, primary_key=True)     parent_id = db.Column(db.Integer, db.ForeignKey("parents.id"))     user = db.relationship("Parent",                        uselist=False,                        foreign_keys=[parent_id]) 

Everything works as expected until I try to db.drop_all() and I get an error that the sqlalchemy.sql.schema.ForeignKeyConstraint name is None. Am I doing something wrong when trying to make this circular one-to-one relationship? I would really like to be able to query just the single column to get the id of the other one, hence the circular reference.

1 Answers

Answers 1

From the SQLAlchemy Docs:

class Parent(Base):     __tablename__ = 'parent'     id = Column(Integer, primary_key=True)     child = relationship("Child", uselist=False, back_populates="parent")  class Child(Base):     __tablename__ = 'child'     id = Column(Integer, primary_key=True)     parent_id = Column(Integer, ForeignKey('parent.id'))     parent = relationship("Parent", back_populates="child") 

Then you can Parent.child or Child.parent all day long

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