Created
February 19, 2015 14:33
-
-
Save rdarder/667610253e2747a5bf8b to your computer and use it in GitHub Desktop.
Self reference foreign key example. Test to check if mysql and sqlite supported DEFERRED constraint checks, turns out not.
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
from sqlalchemy import Column, Integer, ForeignKey, create_engine | |
from sqlalchemy.ext.declarative import declarative_base | |
from sqlalchemy.orm import relationship, Session | |
Base = declarative_base() | |
class Person(Base): | |
__tablename__ = 'persons' | |
id = Column(Integer, primary_key=True) | |
best_friend_id = Column( | |
Integer, | |
ForeignKey('persons.id', use_alter=True, name='fk_best_friend')) | |
#if we wanted to set nullable=False to the foreignkey, we'd need an engine with | |
# DEFERRED constraing checks support | |
best_friend = relationship( | |
'Person', | |
primaryjoin='Person.best_friend_id==Person.id', | |
post_update=True, | |
foreign_keys=[best_friend_id], | |
uselist=False | |
) | |
engine = create_engine('sqlite:///') | |
session = Session(bind=engine) | |
Base.metadata.create_all(bind=engine) | |
guy1 = Person() | |
guy1.best_friend = guy1 | |
session.add(guy1) | |
session.commit() |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment