Using FastAPI with SQLAlchemy: How to Handle Relationships Correctly When Fetching Data
I'm optimizing some code but I'm currently developing a FastAPI application with SQLAlchemy to manage a simple blog system... I have two models: `User` and `Post`, where each user can have multiple posts. However, when I try to fetch a user along with their posts, I keep encountering issues with the relationships not being populated correctly. Here's a snippet of my code: ```python from sqlalchemy import Column, Integer, String, ForeignKey from sqlalchemy.orm import relationship from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() class User(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True) name = Column(String) posts = relationship('Post', back_populates='user') class Post(Base): __tablename__ = 'posts' id = Column(Integer, primary_key=True) title = Column(String) content = Column(String) user_id = Column(Integer, ForeignKey('users.id')) user = relationship('User', back_populates='posts') ``` When I try to fetch a user with their posts using this endpoint: ```python @app.get('/users/{user_id}') async def get_user(user_id: int, db: Session = Depends(get_db)): user = db.query(User).filter(User.id == user_id).first() return user ``` I receive a response that looks like this: ```json { "id": 1, "name": "John Doe", "posts": null } ``` I've confirmed that there are indeed posts in the database for the user. I've tried adding `joinedload` to my query like this: ```python from sqlalchemy.orm import joinedload user = db.query(User).options(joinedload(User.posts)).filter(User.id == user_id).first() ``` But I still receive `null` for the `posts` field. I've verified that the foreign key constraints are set up correctly in my database. Is there something I might be missing in terms of configuration or query structure to ensure that the related posts are fetched correctly? Any help would be greatly appreciated! Has anyone else encountered this?