The following is a stripped down example of my app, that does NOT show the
problem:
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship, backref, sessionmaker
from sqlalchemy import Column, Integer, String, ForeignKey
from sqlalchemy import create_engine
Base = declarative_base()
class Release(Base):
__tablename__ = 'releases'
id = Column(Integer, primary_key=True)
version = Column(String, nullable=False)
def __init__(self, version):
self.version = version
def __repr__(self):
return "<Release(version={})>".format(self.version)
class URL(Base):
__tablename__ = 'urls'
id = Column(Integer, primary_key=True)
release_id = Column(Integer, ForeignKey('releases.id'), nullable=False)
url = Column(String, nullable=False)
release = relationship("Release",
cascade="all, delete-orphan",
single_parent=True,
backref=backref('urls', order_by=url))
def __repr__(self):
return "<URL(url={})>".format(self.url)
def new_release(version, urls):
r = Release(version)
l = []
for url in urls:
u = URL()
u.url = url
l.append(u)
r.urls = l
return r
if __name__ == '__main__':
db = create_engine('sqlite://')
Base.metadata.create_all(db)
Session = sessionmaker(db)
s = Session()
s.merge(new_release('1.0', ['http://myapp.net/1.0']))
s.commit()
The real app is basically just a lot more complex (releases have 4 child
lists like urls, my example adds multiple objects in each list. The app
fails with an integrity error because a url has a null request_id. In
actual fact, the hierarchy all gets built up properly in the end, but it
appears that something is trying to save the children before all of the
links are set up.
If I remove nullable=False from the foreign keys, it works fine.
I think one of the error tracebacks (sorry, I lost them in other output)
mentioned autoflush - could the ORM be trying to flush bits of the
hierarchy before it's complete? Is there a better fix than removing the
nullable=False constraints?
Thanks for any help,
Paul
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