On Apr 24, 2012, at 1:16 PM, David Bowser wrote:
> I have a mixin as follows designed to remove a bunch of copy paste
> relationship code.
>
> class UserMixin(object):
> @_declared_attr
> def user_id(cls):
> return
> sa.Column('user_id',typ.Integer,sa.ForeignKey("tg_user.user_id",
> ondelete="CASCADE"),nullable=False)
>
> @_declared_attr
> def user(cls):
> return orm.relationship("User",primaryjoin='%s.user_id ==
> User.user_id'%cls.__name__)
>
> @_declared_attr
> def user_profile(cls):
> return orm.relationship('UserProfile',primaryjoin="%s.user_id ==
> UserProfile.id"%cls.__name__,
> foreign_keys=lambda:[metadata.tables['user_profiles'].c.id],
> backref=cls.__tablename__ if cls.__tablename__ else
> tablename(cls.__name__))
>
> when I use my mixin in say a class like this:
>
> class JournalEntry(UserMixin,DeclarativeBase):
> __tablename__ = 'journal_entries'
> #{ Columns
> id = Column(Integer,primary_key=True)
> is_private = Column(Boolean,default=False)
> modified = Column(DateTime,onupdate=datetime.datetime.now)
> text = Column(UnicodeText)
> #}
>
> And then I:
>
>>>> from myProject.model import *
>>>> profile = DBSession.query(UserProfile).get(1)
>>>> profile.journal_entries
>
> I keep getting the error:
>
> /Users/Me/Documents/Work/Projects/myProject/myProject/lib/python2.7/site-packages/SQLAlchemy-0.7.6-py2.7-macosx-10.7-intel.egg/sqlalchemy/orm/strategies.py:508:
> SAWarning: Multiple rows returned with uselist=False for lazily-loaded
> attribute 'UserProfile.journal_entries'
> < myProject.model.user_data.JournalEntry object at 0x10d8b26d0>
>
> I can't figure out why it's using uselist=False, and a joined lazy load. Any
> help pointing me in the right direction would be great.
it's probably that foreign_keys in your relationship there, which appears to
refer to user_profiles.c.id. that's the column which is referred to here, and
that parameter would instead be referring to the "user_id" column, i.e. the one
that has the foreign key back to the parent row. It's equivalent to the
column that would have ForeignKey set up on it here; I guess you have some
multiple foreign keys happening here? tg_user.user_id is not the same as
UserProfile.id ? This suggests some potential design problems, what is the
value of JournalEntries.user_id if it points to row "3" in tg_user.user_id and
row "5" in user_profile.id ?
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