sqlalchemy.exc.ArgumentError while running migrations

Question

I am facing an Argument error while trying to run migrations, but I have failed to figure out where the problem is, What am trying to implement is a relationship between two models. Below is my model class :

class TourPackages(db.Model):
    __tablename__ = 'tour_package'

    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(50))
    description = db.Column(db.TEXT)
    price = db.Column(db.Float)
    destination = db.relationship('Destinations', backref='tourpackages', lazy=True)
    capacity = db.Column(db.Integer)

    @property
    def serialize(self):
        return {
            'name': self.name,
            'description': self.destination,
            'price': self.price,
            'destination': self.destination,
            'capacity': self.capacity
        }


class Destinations(db.Model):
    __tablename__ = 'destination'

    id = db.Column(db.Integer)
    location = db.Column(db.String(50))
    danger_type = db.Column(db.String(50))

When I run migrations with the command below:

flask db migrate -m "Initial migration."

I get this error :

sqlalchemy.exc.ArgumentError: Mapper mapped class Destinations->destination could not assemble any primary key columns for mapped table 'destination'

What am I doing wrong here

TheSinisterShadow · Accepted Answer · 2020-07-06 21:59:10Z

1

In your Destinations model, you need to change the id column to be a primary key

id = db.Column(db.Integer, primary_key=True)

and add a foreign key column for the relationship, again in Destinations:

tourpackages_id = db.Column(db.Integer, db.ForeignKey('tour_package.id'))

See the documentation.

answered Jul 6, 2020 at 21:59

TheSinisterShadow

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