ORM Async Tests

A couple of tests checking how SQLAlchemy async works.

How to use it

We use docker compose for the DB and just in case we add other services in the future, like FastAPI which I would love to see it working along with SQLAlchemy.

docker compose up will start the DB and create the default user, password and database.

Then you, after installing Poetry on the system (info here), run poetry install.

Then you can choose:

• Run any script defined in pyproject.toml:

$ poetry run test1

• Run any script from within inside a shell:

$ poetry shell
$ test1

Tools and libraries

We use the following tools:

• docker: With compose, used to create the environment in which everything runs.
• poetry: To manage the project, requirements and venv.
• nox: As a Python replacement of tox, automation tool.
• alembic: To handle DB migrations. Aync support

And the following libraries and Python packages:

• SQLAlchemy: As the ORM.
• asyncpg: To connect to Postgresql.

Nox

Below you can see a list of commands that could help you run usual commands. Each session can receive parameters, for that after the command use -- as a separator between nox parameters and the session ones.

• nox: Runs the default sessions.
• nox -l: Lists the sessions that can be executed.
• nox -s <session>: Executes <session>.

Alembic and DB migrations

Alembic handles the DB migrations. You can see the docs in here. It has support for branches and other more complex stuff that are not used in here because of the simplicity of the tests done. For instance, branches could be used as a way to split migrations from different packages or applications inside the code.

Init

Init requires a template that works in an async way, this is already done because Alembic is only initialized once, but for future reference:

$ alembic init -t async src/alembic

Create a new revision

The following commands creates a new revision. --autogenerate looks for changes in the models and includes them in the migration file.

$ alembic revision --autogenerate -m 'Some message'

See the migration history

$ alembic history

Apply a migration

Apply all migrations

$ alembic upgrade head

To apply up to a specific migration replace head with th revision hash.

Rollback migrations

Rollback the last migration

$ alembic downgrade -1

To rollback to a specific migration replace -1 with the hash of the revision you want.