you need to use the post_update option described at
http://docs.sqlalchemy.org/en/rel_0_7/orm/relationships.html#rows-that-point-to-themselves-mutually-dependent-rows
.
On Jun 6, 2012, at 1:15 AM, Alex Grönholm wrote:
> I have trouble configuring two relationships from one class to another. The
> following code should be fairly self-explanatory:
>
>
> from sqlalchemy import *
> from sqlalchemy.orm import *
> from sqlalchemy.ext.declarative import declarative_base
>
>
> Base = declarative_base()
>
> class Company(Base):
> __tablename__ = 'companies'
> id = Column(Integer, primary_key=True)
> default_address_id = Column(Integer, ForeignKey('addresses.id',
> use_alter=True, name='defaultaddress_fk'))
> addresses = relationship('Address', backref='company',
> primaryjoin='Address.company_id == Company.id')
> default_address = relationship('Address',
> primaryjoin='Company.default_address_id == Address.id')
>
>
> class Address(Base):
> __tablename__ = 'addresses'
> id = Column(Integer, primary_key=True)
> company_id = Column(Integer, ForeignKey(Company.id), nullable=False)
>
>
> engine = create_engine('sqlite:///', echo=True)
> Base.metadata.create_all(engine)
> session = Session(engine)
> company = Company()
> address = Address()
> session.add(company)
> company.default_address = address
> company.addresses.append(address)
> session.flush()
>
>
> What I expect is SQLAlchemy to 1) create the company, 2) create the address
> with the new company's id in company_id, 3) assign the ID of the new address
> to company.default_address_id
> Trouble is, I get this error:
>
> sqlalchemy.exc.CircularDependencyError: Circular dependency detected. Cycles:
> set([ProcessState(ManyToOneDP(Company.default_address), <Company at
> 0x16a7210>, delete=False), ProcessState(ManyToOneDP(Address.company),
> <Address at 0x16ad190>, delete=False), SaveUpdateState(<Company at
> 0x16a7210>), ProcessState(OneToManyDP(Company.addresses), <Company at
> 0x16a7210>, delete=False), SaveUpdateState(<Address at 0x16ad190>)]) all
> edges: set([(ProcessState(OneToManyDP(Company.addresses), <Company at
> 0x16a7210>, delete=False), SaveUpdateState(<Address at 0x16ad190>)),
> (SaveUpdateState(<Address at 0x16ad190>),
> ProcessState(ManyToOneDP(Company.default_address), <Company at 0x16a7210>,
> delete=False)), (SaveUpdateState(<Company at 0x16a7210>),
> SaveUpdateState(<Address at 0x16ad190>)), (SaveUpdateState(<Company at
> 0x16a7210>), ProcessState(ManyToOneDP(Address.company), <Address at
> 0x16ad190>, delete=False)),
> (ProcessState(ManyToOneDP(Company.default_address), <Company at 0x16a7210>,
> delete=False), SaveUpdateState(<Company at 0x16a7210>)),
> (ProcessState(ManyToOneDP(Address.company), <Address at 0x16ad190>,
> delete=False), SaveUpdateState(<Address at 0x16ad190>)),
> (SaveUpdateState(<Company at 0x16a7210>),
> ProcessState(OneToManyDP(Company.addresses), <Company at 0x16a7210>,
> delete=False))])
>
> What am I doing wrong? I had a similar problem in my production app when
> trying to delete a Company that had a default address assigned.
> I'm on SQLAlchemy 0.7.7.
>
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