Using Alembic API from inside application code

Question

I am using SQLite as an application file format (see here for why you would want to do this) for my PySide-based desktop application. That is, when a user uses my app, their

Answer 1

For anyone else trying to achieve a flyway-esque result with SQLAlchemy, this worked for me:

Add migration.py to your project:

from flask_alembic import Alembic

def migrate(app):
    alembic = Alembic()
    alembic.init_app(app)
    with app.app_context():
        alembic.upgrade()

Call it on application startup after your db has been initialized

application = Flask(__name__)
db = SQLAlchemy()
db.init_app(application)
migration.migrate(application)

Then you just need to do the rest of the standard alembic steps:

Initialize your project as alembic

alembic init alembic

Update env.py:

from models import MyModel
target_metadata = [MyModel.Base.metadata]

Update alembic.ini

sqlalchemy.url = postgresql://postgres:postgres@localhost:5432/my_db

Assuming your SQLAlchemy models are already defined, you can autogenerate your scripts now:

alembic revision --autogenerate -m "descriptive migration message"

If you get an error about not being able to import your model in env.py, you can run the following in your terminal fo fix

export PYTHONPATH=/path/to/your/project

Lastly, my migration scripts were getting generated in the alembic/versions directory, and I had to copy them to the migrations directory for alembic to pick them up.

├── alembic
│   ├── env.py
│   ├── README
│   ├── script.py.mako
│   └── versions
│       ├── a5402f383da8_01_init.py  # generated here...
│       └── __pycache__
├── alembic.ini
├── migrations
│   ├── a5402f383da8_01_init.py  # manually copied here
│   └── script.py.mako

I probably have something misconfigured, but it is working now.