it seems like a small bug and you can file a ticket for that, but the
intent is that you'd be using None to represent NULL in the general
case.
On May 19, 2009, at 11:21 AM, klaus wrote:
>
> 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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