FastAPI: How to handle multiple asynchronous database calls with SQLAlchemy without blocking?
I'm dealing with I'm building a feature where I'm building a FastAPI application using SQLAlchemy for database interactions, and I'm working with a important slowdown when making multiple asynchronous database calls... I want to fetch user data along with their associated profiles and preferences in a single request without blocking the event loop. I tried using `asyncio.gather` to run the calls concurrently, but I'm still seeing performance optimization and sometimes running into the following behavior: ``` RuntimeError: Task <Task pending name='Task-4' coro=<Session.close() running at /usr/local/lib/python3.8/site-packages/sqlalchemy/orm/session.py:1214> cb=[_run_until_complete_cb()]> got Future <Future pending> attached to a different loop ``` Here's a simplified version of what I'm trying to achieve: ```python from fastapi import FastAPI, Depends from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, sessionmaker from sqlalchemy.ext.declarative import declarative_base import asyncio DATABASE_URL = "postgresql+asyncpg://user:password@localhost/dbname" engine = create_async_engine(DATABASE_URL) AsyncSessionLocal = sessionmaker(bind=engine, class_=AsyncSession, expire_on_commit=False) Base = declarative_base() app = FastAPI() async def get_db(): async with AsyncSessionLocal() as session: yield session @app.get("/user/{user_id}") async def read_user(user_id: int, db: AsyncSession = Depends(get_db)): user = await db.execute(select(User).filter_by(id=user_id)) profile = await db.execute(select(Profile).filter_by(user_id=user_id)) preferences = await db.execute(select(Preferences).filter_by(user_id=user_id)) return { "user": user.scalar(), "profile": profile.scalar(), "preferences": preferences.scalar() } ``` I've also read through the FastAPI and SQLAlchemy documentation but haven't found a clear solution to optimize these calls. Any advice on how to properly manage async database calls in this context would be greatly appreciated! I'm using Python 3.10 in this project. Is this even possible? Is this even possible? I'm on Windows 10 using the latest version of Python. Any examples would be super helpful.