Flask-migrate: How to call apis(upgrade, current) in python script

[zhangjiajie023]

I have a database db. I want to judge if flask_migrate has created tables in db. If not, upgrade db.
There are commands, but no examples about calling migrate, upgrade in python script.
The test files in flask_migrate also run commands, such as:
(o, e, s) = run_cmd('python app.py db migrate')

[miguelgrinberg]

The tests are based on the most common usage, which is people running the commands manually from the shell.

But all commands have an API version, which is documented here: https://flask-migrate.readthedocs.io/en/latest/#api-reference. For an example, see https://github.com/miguelgrinberg/flasky/blob/master/manage.py#L67-L71.

You can also use the Alembic API if you need low level access.

[dradux]

If anyone else lands here searching for a way to run migrations on start of your app (e.g. useful for containerized flask apps) here is how I do it:

...
from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate
...
db = SQLAlchemy(app)
migrate = Migrate(app, db)
# apply any/all pending migrations.
with app.app_context():
  from flask_migrate import upgrade as _upgrade
  _upgrade()

Take caution to ensure that you handle migrations and corresponding app code in a manner that works with migrations being applied on start of the app (e.g. if you have multiple instances of your app running in a containerized/load balanced manner make sure one updating of one of the containers does not break other containers).

[snixon]

If you're curious how to run flask db init/migrate/upgrade from a click command...

import click
from flask.cli import with_appcontext
from flask_migrate import init, migrate, upgrade
...
@click.command()
@with_appcontext
def setup_db():
    init_db = init()
    migrate_db = migrate()
    upgrade_db = upgrade()

Then you'd call this at the CLI with:

flask setup_db