On Sep 5, 2008, at 1:48 PM, Alex K wrote:
>
> Hi All,
>
> I'm using sqlalchemy and mod_wsgi. mod_wsgi is set up to serve request
> in multiple threads of the same process.
>
> class looks like that:
>
> class WebSessionRoute(DeclarativeBase):
>
> __tablename__ = 'web_session_route'
>
> key = Column('key', Unicode(40), primary_key=True)
> user_id = Column('user_id',Integer, ForeignKey('user_route.id')),
> expires = Column('expires', DateTime)
>
> def __init__(self,key,user_id,expires):
> self.key = key
> self.user_id = user_id
> self.expires = expires
>
>
> I'm facing the following issue. The first request goes fine, but on
> the second attempt I get:
>
> query.py, line 1620, in __init__
> raise sa_exc.InvalidRequestError("Invalid column expression '%r'"
> % column)
>
> on any attempt to execute any query. Instrumented attributes are in
> place, but they don't work.
> I've rewrote the code using regular mapper. If each thread maps the
> class to the table. everything is ok,
> Once I put the lock to make initialization only once per process, I
> get this error.
>
> I would appreciate any feedback from you,
> Thanks in advance,
>
this mostly depends on how you've configured Session access. Your
mappers, classes, and database engine should be configured at the
application level only, not per request, and you should be using
scoped_session() to manage one session per thread.
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