[Sqlalchemy-tickets] Issue #3080: load_only triggers `sqlalchemy.exc.NoSuchColumnError` if primary key is not included on subqueryload (zzzeek/sqlalchemy)

[jvanasco <iss...@bi...>]

New issue 3080: load_only triggers `sqlalchemy.exc.NoSuchColumnError` if primary key is not included  on subqueryload
https://bitbucket.org/zzzeek/sqlalchemy/issue/3080/load_only-triggers

jvanasco:

example attached below; this happens in 0.9.4

if trying to load_only a column of the child relationship and not passing in the primary_key, sqlalchemy isn't happy

the sql generated is fine and runs -- it pulls the specified column and uses query string as an anonymous column ( sidenote: is that really necessary ?)

but the ORM is unhappy and raises an error.  

adding the primary key works.  

using a joinedload instead of subqueryload works as well.

and hey, i made a proper test case!


    from sqlalchemy import *
    from sqlalchemy.orm import *
    from sqlalchemy.ext.declarative import declarative_base

    Base = declarative_base()

    class TableA(Base):
        __tablename__ = 'table_a'
        id = Column(Integer, primary_key=True)
        name = Column(String(50))

        bs = relationship("TableB", primaryjoin="TableB.table_a_id==TableA.id")

    class TableB(Base):
        __tablename__ = 'table_b'
        id = Column(Integer, primary_key=True)
        name = Column(String(30))
        table_a_id = Column(Integer, ForeignKey('table_a.id'), nullable=False)


    e = create_engine("sqlite://", echo=True)
    Base.metadata.create_all(e)

    s = Session(e)

    s.add_all([
        TableA(id=1, name='a',),
        TableA(id=2, name='aa',),
        TableA(id=3, name='aaa',),
        TableA(id=4, name='aaaa',),
        TableB(id=1, name='b', table_a_id=1),
        TableB(id=2, name='aa', table_a_id=2),
        TableB(id=3, name='aaa', table_a_id=3),
        TableB(id=4, name='aaaa', table_a_id=4),
    ])

    s.commit()


    q = s.query( TableA ).filter( TableA.id == 2 )

    ## this passes
    q_good = q.options( subqueryload('bs').load_only('id','name') )
    print "trying q_good"
    result = q_good.first()

    q_bad = q.options( subqueryload('bs').load_only('name') )
    print "trying q_bad"
    result = q_bad.first()

    s.close()