Sqlalchemy AmbiguousForeignKeysError?

Question

PostgreSQL

class User(Base):
    __tablename__ = '_users'
    id = Column(String(), primary_key=True)
    firstname = Column(String(100))
    lastname = Column(String(100))
    reg_date = Column(DateTime(), server_default=text('CURRENT_TIMESTAMP'))
    transactions = relationship('InnerTransaction')

class InnerTransaction(Base):
    __tablename__ = '_transactions'
    id = Column(Integer(), primary_key=True, autoincrement=False)
    sender_id = Column(String(), ForeignKey('_users.id'))
    receiver_id = Column(String(), ForeignKey('_users.id'))
    amount = Column(String())
    created_at = Column(DateTime(), server_default=text('CURRENT_TIMESTAMP'))

These models correctly create tables, but when accessing the tables, an error occurs:

Exception has occurred: AmbiguousForeignKeysError
Could not determine join condition between parent/child tables on relationship User.transactions - there are multiple foreign key paths linking the tables. Specify the 'foreign_keys' argument, providing a list of those columns which should be counted as containing a foreign key reference to the parent table.

There are similar examples in the documentation, but I didn’t figure out how to apply them in my case.

How to correctly organize the relationship of tables with several foreign keys?

Answer 1

There is an example in the documentation. There is not a similar, but exactly the same case:
https://docs.sqlalchemy.org/en/14/orm/join_conditi...