How to Use Async SQLAlchemy in FastAPI

In this video, I'll demonstrate how to use async Sqlalchemy in FastAPI by converting an existing sync version of Sqlalchemy to Async.

[gerardorosiles]

Thanks for the explanation. Illustrating a more complex query and a full CRUD example would be great.

[jijojoseph]

can you help in how we can integrate alembic into this

[ineps]

in this approach will be one Session per request?

[Iamjafex]

Good overview! I agree with your distaste of the new sql alchemy approach. I've used pre 2.0 for a few years now and have found it very easy and comfortable, but I do see the benefit of this approach in verbosity. Hopefully it'll make stuff like joins and other weird query gimmicks easier than the old approach

[SAsquirtle]

instead of doing

results = await db.execute(select(User))
users = results.scalars().all()

you can also do this if it makes it look any better

users = await db.scalars(select(User))
users = users.all()

[default_youtube_profile]

aiomysql extension for sqlalchemy does not have async_sessionmaker! what should I use?

[mauricioyepes]

Great video, thank you. What do you think about using asyncio?
result = await asyncio.gather(*tasks)

And tasks could be like:
tasks = [get_users()]

In that way you don't need to change the logic to access the DB, the responsibility for converting the get_users to async will be for asyncio. This may work for projects that already have a lot of logic using sync access to the DB so they don't need to refactor all the logic they have to access the DB.

[salmanmushtaq]

Can we use same for production? Also what will be the driver for postgresql?

[Learn_with_cosmos]

Nice one. I am coming back to python after years of NodeJS and others lol!

[sampri]

Is there one session per request in this example?

[ReRubis]

Is putting base.metadata.create_all method in function returning session a good approach?
Isn't it gonna run everytime you init session, which occurs on every endpoint?
And it's run_sync. Doesn't seem efficient.
I think it should be separated into a separate function and ran once on the app startup, no?

[uclmpwx]

Great video,
Actually, I have an question.
when I use AsyncSession and call await db.execute(""" some procedures """) and that result of the procedure is multiple result sets.
so how to get several sets?

[danielfajt]

Does this solution cover a rollback? get_db() -> AsyncSession, on which you will use transaction eventually. If you call flush() somewhere in the call stack and an exception is raised, this won't call a rollback, right? Thanks.

[Useroftherisingsun]

I understand that nobody's probably gonna answer me soon here, but I don't understand why metadata.create_all() is placed into get_db() function. Like, isn't create_all() method is should only be used once while creating database, not when accesing it?

[CodeTesting-pdtd]

Would you happen to know if using the @asynccontextmanager decorator from the built-in contextlib is of any use when creating AsyncSession objects?

According to the SQLAlchemy documentation, it seems that the async_sessionmaker is already handling the teardown.

I am having trouble deciding if I should use the asynccontextmanager or not.

[moneeshkumar]

Is it safe to use Aync SQLAlchemy, do we run into race conditions and Is it production safe?
Kindly reply

[joaovictor-dlve]

What's the difference using async db and sync db? like, if I want I can use SYNC sqlalchemy with ASYNC fastapi, right?

[joaovictor-dlve]

Can I use migrations with sqlalchemy assincronous?

[wattsfield]

That's weird, my AsyncSession does not have the .query()

[fumano]

Ill just stick to synchronous computing, if i wanted efficiency i would use rust and not python :)