Migrations solve a dangerous problem:

• your models change over time
• your database schema must change too
• you need a safe, repeatable way to apply those changes

Flask-Migrate wraps Alembic to manage migrations.

Install

pip install Flask-Migrate

pip install Flask-Migrate

Setup

from flask_migrate import Migrate
 
migrate = Migrate(app, db)

from flask_migrate import Migrate
 
migrate = Migrate(app, db)

Typical workflow

1. Initialize migrations folder:

flask db init

flask db init

2. Create a migration script:

flask db migrate -m "create users table"

flask db migrate -m "create users table"

3. Apply it:

flask db upgrade

flask db upgrade

Key idea

• migratemigrate generates migration scripts from model diffs
• upgradeupgrade applies them to the database

Best practices

• review generated scripts before applying
• commit migrations to git
• run migrations in CI/staging before production