On Feb 12, 2011, at 2:15 AM, cd34 wrote:
> I'm trying to pass a value to a relation at runtime rather than
> instantiation time. I've got the callable working with a fixed value,
> but, in reading the docs over the last few days , I'm either not
> finding the proper incantation or the right terms in the documentation
> to figure out what I'm trying to do.
>
> The barest example code I can write that demonstrates what I'm trying
> to do:
>
> #!/usr/bin/python2.6
>
> import sqlalchemy
>
> from sqlalchemy import create_engine
> from sqlalchemy import Column
> from sqlalchemy import Unicode
> from sqlalchemy import ForeignKey
> from sqlalchemy import and_
>
> from sqlalchemy.orm import relationship
> from sqlalchemy.orm import mapper
> from sqlalchemy.orm import sessionmaker
> from sqlalchemy.orm import backref
>
> from sqlalchemy.ext.declarative import declarative_base
> Base = declarative_base()
>
> engine = create_engine('sqlite:///:memory:', echo=True)
> metadata = Base.metadata
>
> class AuthUser(Base):
> __tablename__ = 'auth_users'
>
> id = Column(sqlalchemy.Integer(unsigned=True), primary_key=True,
> autoincrement=True)
>
> class NewsVoteLog(Base):
> __tablename__ = 'news_vote_log'
>
> id = Column(sqlalchemy.Integer(unsigned=True), primary_key=True,
> autoincrement=True)
> user_id = Column(sqlalchemy.Integer(unsigned=True),
> ForeignKey(AuthUser.id))
> ncid = Column(sqlalchemy.Integer( unsigned=True),
> ForeignKey('news_comments.id'))
>
> def __repr__(self):
> return 'NewsVoteLog <id: %s user_id: %s ncid: %s>' %
> (self.id,
> self.user_id, self.ncid)
>
> def callable_user_id():
> return 1
>
> class NewsComment(Base):
> __tablename__ = 'news_comments'
>
> id = Column(sqlalchemy.Integer(unsigned=True), primary_key=True,
> autoincrement=True)
> parent_id = Column(sqlalchemy.Integer(unsigned=True),
> ForeignKey('news_comments.id'), default=0)
> title = Column(Unicode(120))
>
> #votes = relationship('NewsVoteLog',
> backref=backref('news_vote_log'), remote_side=NewsVoteLog.ncid)
> votes = relationship('NewsVoteLog',
> backref=backref('news_vote_log'),
> primaryjoin=and_(NewsVoteLog.ncid==id,
> NewsVoteLog.user_id==callable_user_id),
> foreign_keys=[NewsVoteLog.ncid, NewsVoteLog.user_id])
>
> metadata.create_all(engine)
>
> DBSession = sessionmaker(bind=engine)()
>
> user = AuthUser()
> DBSession.add(user)
> user2 = AuthUser()
> DBSession.add(user2)
> user3 = AuthUser()
> DBSession.add(user3)
>
> news = NewsComment(parent_id=0, title='test article')
> DBSession.add(news)
>
> DBSession.flush()
>
> vote1 = NewsVoteLog(user_id=user.id, ncid=news.id)
> DBSession.add(vote1)
> vote2 = NewsVoteLog(user_id=user2.id, ncid=news.id)
> DBSession.add(vote2)
> vote3 = NewsVoteLog(user_id=user3.id, ncid=news.id)
> DBSession.add(vote3)
>
>
> DBSession.flush()
>
> #test_record =
> DBSession.query(NewsComment).filter(NewsComment.id==1).one()
> test_record =
> DBSession.query(NewsComment).filter(NewsComment.id==1).params(uid=1).one()
> print test_record.votes
>
>
> What I would like to do is pass uid at runtime. I hacked it together
> with an outerjoin, but, as the child records are a relation from the
> parent, only the parent received the outerjoin.
What's making this hard to follow is that "uid" is only referenced in your
Query below and I don't see any other mention of what "uid" is.
There's a recipe for the general idea of passing binds to relationship at
http://www.sqlalchemy.org/trac/wiki/UsageRecipes/GlobalFilter . The
elaborate side of it is when the relationship is lazily loading, you have to
store your bind parameter in the lazyloader itself, hence the TemporalLoader
class in that recipe.
>
> If someone can point me to the documentation or name the concept I'm
> looking for, I'd appreciate it. Thanks.
>
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