sqlalchemy.exc.ProgrammingError: (psycopg2.errors.DuplicateObject) type "orderstatus" already exists. Is the problem in my model or in my database?

Question

I am developing a flask microservice application. I get this issue when I use the command flask db migrate the database. I want to use OrderStatus class inside Enum function. I couldn't find the reason for this. Is the problem in my model or in my database configuration?

class OrderStatus(enum.Enum):
    new = "NEW"
    preparing = "PREPARING"
    on_the_way = "ON THE WAY"
    delivery = "DELIVERED"
    cancel = "CANCEL"

class Order(db.Model):
    """  Orders model for storing menu related data """
    __tablename__ = 'order'
    id = db.Column(db.Integer, primary_key=True)
    order_id = db.Column(db.String(256),index=True)
    user_id = db.Column(db.Integer, db.ForeignKey('user.id'), index=True)
    menu_id = db.Column(db.Integer, db.ForeignKey('menu.id'), index=True)
    restaurant_id = db.Column(db.Integer, db.ForeignKey('restaurant.id'), index=True)
    status = db.Column(db.Enum(OrderStatus), default="New")
    created_on = db.Column(db.DateTime, default=datetime.utcnow)```

Answer 1

This problem is on your migration. Alembic revision --autogenerate create a wrong downgrate op, and don't drop the object enum on downgrate.

Create enum var outside of def upgrade

enum_type = sa.Enum("ONE", "TWO", "THREE", name="enum")

and update the column:

sa.Column("enum", enum_type, nullable=True)

On def downgrade add this line:

enum_type.drop(op.get_bind(), checkfirst=False)