Hi there,
I'm having an issue when building queries against a relationship using a
custom primaryjoin.
The issue can be reproduced with a slightly modified Users/Address model as
taken from the docs:
from sqlalchemy import Integer, ForeignKey, String, Column
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship
Base = declarative_base()
class User(Base):
__tablename__ = 'user'
id = Column(Integer, primary_key=True)
name = Column(String)
address_id = Column(Integer, ForeignKey('address.id'))
boston_address = relationship("BostonAddress",
primaryjoin="and_(User.address_id==Address.id, "
"Address.city=='Boston')")
class Address(Base):
__tablename__ = 'address'
__mapper_args__ = {'polymorphic_on': 'type',
'polymorphic_identity': 'any'}
id = Column(Integer, primary_key=True)
type = Column(String, primary_key=True)
street = Column(String)
city = Column(String)
state = Column(String)
zip = Column(String)
class BostonAddress(Address):
__mapper_args__ = {'polymorphic_on': 'type',
'polymorphic_identity': 'Boston'}
The actual application uses more than one Address subclass obviously - but
the above suffices for the example.
When trying to query for "Users not having a boston_address" I'd use
User.boston_address == None
as a where clause, which however turns out be become:
"user".address_id IS NULL AND 'Boston' IS NULL
which obvisouly won't yield any results - I'm not sure though, whether this
is a bug or simply due to the maybe unusual model.
I've now implemented a dedicated comparator for this type of relationship
which seems to work.
But still I'm wondering if there's an easier way to fix this, e.g. by
annotating parts of the join condition as "do not touch"...?
Cheers
Sebastian
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