Why is my FastAPI endpoint returning an empty response for an async database query?
I've looked through the documentation and I'm still confused about I'm working on a FastAPI application where I need to fetch user data from a PostgreSQL database asynchronously. However, when I hit the endpoint, I receive an empty JSON response, and I'm not sure why. Here's a simplified version of my code: ```python from fastapi import FastAPI, HTTPException from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine from sqlalchemy.orm import sessionmaker, declarative_base from sqlalchemy import Column, Integer, String, select DATABASE_URL = "postgresql+asyncpg://user:password@localhost/dbname" engine = create_async_engine(DATABASE_URL) Base = declarative_base() class User(Base): __tablename__ = "users" id = Column(Integer, primary_key=True) name = Column(String) email = Column(String) async_session = sessionmaker(engine, class_=AsyncSession, expire_on_commit=False) app = FastAPI() @app.get("/users/{user_id}") async def get_user(user_id: int): async with async_session() as session: query = select(User).where(User.id == user_id) result = await session.execute(query) user = result.scalars().first() if user: return user raise HTTPException(status_code=404, detail="User not found") ``` When I access `/users/1`, I always receive an empty response, even though I know there is a user with that ID in the database. I've checked the connection settings, and they seem correct. I also verified that the table exists and contains the data. To debug, I added print statements inside the `get_user` function, and it seems like the query runs fine, but the `scalars().first()` method returns `None` consistently. I've tried various variations of the query and even hard-coded a user to check if it was fetching anything at all, but I still get nothing. Could this be a question with the way the async session is being handled, or is there something in my query that I'm missing? Any insights would be greatly appreciated! For context: I'm using Python on Windows. My development environment is Ubuntu. This is for a application running on Linux. Hoping someone can shed some light on this. My development environment is Ubuntu 20.04. Any ideas what could be causing this?