On Aug 25, 2010, at 4:57 PM, Nigel wrote:
> Hi all,
>
> I'm having some trouble with using a schema with a many-to-many
> declarative mapping. The error i'm getting is as follows:
>
> "
> sqlalchemy.exc.InvalidRequestError: One or more mappers failed to
> compile. Exception was probably suppressed within a hasattr() call.
> Message was: One or more mappers failed to compile. Exception was
> probably suppressed within a hasattr() call. Message was: When
> compiling mapper Mapper|Entity|entity, expression 'Entity.id ==
> entityConnections.c.masterId' failed to locate a name ("name
> 'entityConnections' is not defined"). If this is a class name,
> consider adding this relationship() to the <class '__main__.Entity'>
> class after both dependent classes have been defined.
> "
>
>
> Here is a bit of code that will fail. Please excuse the word wrapping:
>
> "
> Base = declarative_base( bind = engine )
>
> entityConnection = Table( 'entityConnections', Base.metadata,
> Column( 'masterId', Integer,
> ForeignKey( 'relationalSchema.entity.id' ), primary_key = True ),
> Column( 'slaveId', Integer,
> ForeignKey( 'relationalSchema.entity.id' ), primary_key = True ),
> schema = 'relationalSchema' )
>
>
> class Entity( Base ):
> __tablename__ = 'entity'
> __table_args__ = { 'schema':'relationalSchema' }
>
> id = Column( Integer, primary_key = True )
> entityType = Column(String)
>
>
> connections = relationship( 'Entity', secondary = entityConnection,
> primaryjoin = "Entity.id == entityConnections.c.masterId",
> secondaryjoin = "Entity.id == entityConnections.c.slaveId",backref =
> 'entity' )
>
> def __init__(self, entityType ):
> self.entityType = entityType
>
> def __repr__(self):
> return "<Entity('%s')>" % ( self.entityType )
>
>
> from sqlalchemy.orm import sessionmaker
> Session = sessionmaker(bind=engine)
> session = Session()
> session.add( Entity( 'test' ) )
> "
>
> If I remove the references to the schema the code runs fine. Adding
> the schema to the primaryjoin and secondaryjoin just changes the error
> so it must be something else. Any ideas what I'm doing wrong here?
> I'm a rank newbie with sqlalchemy so it's probably a pretty easy thing
> to fix!
er OK you're actually doing something that has not been anticipated, and it is
the "relationalSchema" bit. So this is a bug/feature type thing in
SQLAlchemy (would have to figure out how we'd like this to work - I've added
ticket #1893 which would have it work as "relationalSchema_entityConnections").
The two workarounds at the moment are:
Base.metadata.tables['entityConnections'] = entityConnection
or, this is certainly easier in this case, just lose the quotes:
connections = relationship( 'Entity', secondary = entityConnection,
primaryjoin = id == entityConnection.c.masterId,
secondaryjoin = id == entityConnection.c.slaveId,backref =
'entity' )
>
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