I have the following code:
from sqlalchemy import *
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import Session, relationship, backref
e = create_engine('sqlite:////tmp/test.db', echo=True)
Base = declarative_base()
Base.metadata = MetaData(e)
class Node(Base):
__tablename__ = 'nodes'
id = Column(Integer, primary_key=True)
class Item(Base):
__tablename__ = 'items'
id = Column(Integer, primary_key=True)
node_id = Column(Integer, ForeignKey(Node.id))
item_type = Column(String(24), default='item')
node = relationship(Node, lazy=True, uselist=False,
backref=backref('objects', lazy=True, uselist=True))
__mapper_args__ = {
'polymorphic_identity': 'item',
'polymorphic_on': 'item_type',
'with_polymorphic': '*',
}
class PolyItem(Item):
__tablename__ = 'poly_items'
id = Column(Integer, ForeignKey(Item.id), primary_key=True)
__mapper_args__ = {
'polymorphic_identity': 'polyitem',
}
item = relationship(Item, lazy=True)
if __name__ == '__main__':
Base.metadata.drop_all()
Base.metadata.create_all()
node = Node()
item = PolyItem(node=node)
session = Session(e)
session.add(node)
session.add(item)
session.commit()
node = session.query(Node).first()
session.delete(node)
session.commit()
This runs fine in 0.7.9 and 0.8.0. However, if I change PolyItem.item to
relationship(Item, lazy=False), 0.7.9 continues to function, while 0.8.0
and 0.8.1 go into infinite loops and eventually fail due to maximum
recursion exceeded. The adding to the db works, it's the delete that is
failing.
I've already worked around it on my end (lazy=False seems of little use
here, and was being added programatically, so I adjusted it there and it
seems okay), but I figured I'd point it out as the behavior changed pretty
radically between those 2 versions.
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