What am I doing wrong in my SQLAlchemy model and column property?

Question

In my Flask + SQLAlchemy application I have - besider others - these two DB tables/models:

class Client(db.Model):
    __tablename__ = "clients"

    id = Column(Integer, primary_key=True)
    client_name = Column(String, nullable=False, unique=True)
    information = Column(String)

class ImageDataSet(db.Model):
    __tablename__ = "image_data_sets"

    id = Column(Integer, primary_key=True)
    client_id = Column(Integer, ForeignKey("clients.id"), nullable=False)

    client = db.column_property(db.select([Client.client_name]).where(Client.id == client_id))

So in other words I want to have an attribute client in my model ImageDataSets , based on the client_id from the Client model/table. This works, however, when starting the application I get the following warning for my call to db.column_property :

SAWarning: implicitly coercing SELECT object to scalar subquery; please use the.scalar_subquery() method to produce a scalar subquery.

Any ideas what I am doing wrong here?

Answer 1

Thanks to Ilja Everilä's comment I solved this by changing the column property to the following:

client = db.column_property(db.select([Client.client_name]).where(Client.id == client_id).scalar_subquery())

Now the warning is gone.