Flask-SQLAlchemy relationship query not returning expected results with lazy loading in Flask 2.1
I've been struggling with this for a few days now and could really use some help. Could someone explain I'm working with an scenario with a Flask application that uses SQLAlchemy for ORM. I have two models, `User` and `Post`, with a one-to-many relationship. When I try to access the posts of a user, the query returns an empty list even though there are posts associated with that user in the database. Here are the model definitions: ```python from flask_sqlalchemy import SQLAlchemy db = SQLAlchemy() class User(db.Model): id = db.Column(db.Integer, primary_key=True) username = db.Column(db.String(80), unique=True, nullable=False) posts = db.relationship('Post', backref='author', lazy=True) class Post(db.Model): id = db.Column(db.Integer, primary_key=True) title = db.Column(db.String(120), nullable=False) user_id = db.Column(db.Integer, db.ForeignKey('user.id'), nullable=False) ``` I am trying to retrieve a user along with their posts using the following code: ```python @app.route('/user/<int:user_id>') def get_user(user_id): user = User.query.get(user_id) return {'username': user.username, 'posts': [post.title for post in user.posts]} ``` When I hit the endpoint `/user/1`, the output is: ``` { "username": "john_doe", "posts": [] } ``` I confirmed that the user with `id=1` exists and that there are posts associated with this user in the database. I even tried forcing a query with `user.posts.all()` and got the same empty result. I've also checked if there are issues with my database session management, but I think that should be fine since I'm using Flask-SQLAlchemy’s built-in session management. I suspect it might be related to the lazy loading configuration but I'm unsure. Any ideas on what could be going wrong here? I recently upgraded to Python latest. This issue appeared after updating to Python stable.