Hi!
Here is a small (and not very useful) example to demonstrate the
problem. A table "user" contains a reference to itself (so that I
don't need a second table). This foreign key translates to a relation.
When I compare the corresponding attribute to null(), I get a
traceback. It all works if I compare it to None instead.
from sqlalchemy.engine import create_engine
from sqlalchemy.schema import MetaData, Table, Column, ForeignKey
from sqlalchemy.types import Integer
from sqlalchemy.orm import mapper, relation, create_session
from sqlalchemy.sql import null
engine = create_engine("postgres://...")
metadata = MetaData(engine)
user = Table("user", metadata,
Column("id", Integer, nullable=False, primary_key=True),
Column("fk", Integer, ForeignKey("public.user.id")),
schema="public", useexisting=True, autoload=False)
class User(object):
pass
mapper(User, user, properties={"ref": relation(User, uselist=False)})
metadata.create_all()
session = create_session()
print session.query(User).filter(User.ref == null()).all()
metadata.drop_all()
(The last line is not executed.)
Here's the traceback:
Traceback (most recent call last):
File "sqlatest.py", line 24, in ?
print session.query(User).filter(User.ref == null()).all()
File "/home/barthelmannk/PortaleHeadZope/sandbox/eggs/
SQLAlchemy-0.5.4p1-py2.4.egg/sqlalchemy/sql/expression.py", line 1253,
in __eq__
return self.operate(operators.eq, other)
File "/home/barthelmannk/PortaleHeadZope/sandbox/eggs/
SQLAlchemy-0.5.4p1-py2.4.egg/sqlalchemy/orm/attributes.py", line 120,
in operate
return op(self.comparator, *other, **kwargs)
File "/home/barthelmannk/PortaleHeadZope/sandbox/eggs/
SQLAlchemy-0.5.4p1-py2.4.egg/sqlalchemy/orm/properties.py", line 492,
in __eq__
return _orm_annotate(self.property._optimized_compare(other,
adapt_source=self.adapter))
File "/home/barthelmannk/PortaleHeadZope/sandbox/eggs/
SQLAlchemy-0.5.4p1-py2.4.egg/sqlalchemy/orm/properties.py", line 623,
in _optimized_compare
value = attributes.instance_state(value)
AttributeError: '_Null' object has no attribute '_sa_instance_state'
Cheers
Klaus
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