On Thu, Aug 9, 2018 at 2:16 PM, wrote:
> One "exit-hatch" for using the SQLAlchemy ORM with asyncio is to use
> executors. In this model, all database access is confined to a thread that
> is not the thread where the eventloop is running.
>
> However, it appears that sessions (thus, transactions) should not span more
> than one executor, meaning that all SQL work must be batched into the same
> executor – right?.
I don't see why that would be the case, as long as these executors
(which I assume are each individual threads) are not executed
concurrently for a particular session.
>
> For a web framework, this is problematic: during the request lifecycle there
> are many points at which the database might need to be accessed (auth
> middleware, request handling, etc.) – hence multiple entries into an
> executor and therefore incompatible with the idea of a session.
should not be the case, a single web request is still doing each of
its steps in serial so the concept of a transaction / session that
spans the full request is compatible with asyncio. Different
executors run concurrently however each of them are local to different
requests with their own session/transaction so there is no issue.
>
> A possible alternative then appears to be using something like `aiopg` and
> confining your work to SQLAlchemy core. However, my problem here is that I'm
> worried by using SQLAlchemy core, and mapping ResultProxy objects into POPO
> (plain old python objects, perhaps built on top of the `attrs` library), I'm
> just ultimately approximating the reinvention of an ORM (without unit of
> work, without relationships, etc.) – right?.
>
> Can someone help me square into my head whether I should be building an
> application on top of sqlalchemy.core (perhaps with something like `aiopg`),
> or whether there is a pattern I'm missing?
If you know me at all, the only pattern you may be missing is that
there's very little value to using asyncio for just about anything IMO
:).But I know that's likely not constructive for your use case.
See http://techspot.zzzeek.org/2015/02/15/asynchronous-python-and-databases/
for my overall take on asyncio which has not changed much since then.
>
> Thanks,
> Devin
>
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