Setting up Flask Migrations
Migrations are needed for easy database changes, so that our data is not affected from any database changes
After setting up flask-sqlalchemy we can do database migrations, that makes the process alot user when shifting to a new database like sqlite, mysql or postgres. Also ensures that our data is safe.
run.py
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
app = Flask(__name__)
app.config.from_object('config')
db = SQLAlchemy(app)
@app.route('/')
def hello_world():
return jsonify({'Home': 'Hello World'})
if __name__ == "__main__":
app.run()
We need to tell flask about our app, so that we can run the app using flask command
$ export FLASK_APP=run.py
We will be using some Plugins for our database migrations
Install using pip
$ pip install Flask-Migrate
$ pip install Flask-Script
Now we need to config the managers in a manage.py for the migrations
manage.py
from myapp import app, db
from flask_script import Manager
from flask_migrate import Migrate, MigrateCommand
import os
app.config.from_object('YOUR_APPLICATION_ENV_VARIABLE')
MIGRATION_DIR = os.path.join('myapp', 'migrations')
migrate = Migrate(app, db, directory=MIGRATION_DIR)
manager = Manager(app)
manager.add_command('db', MigrateCommand)
## we need to add models for our database
class User(db.Model):
__tablename__ = 'user'
email = db.Column(db.String(100), unique=True, nullable=False)
password = db.Column(db.String(8), nullable=False)
def __init__(self, email, password):
self.email = email
self.password = password
if __name__ == '__main__':
manager.run()
Now we need to initiate migrations using :
$ python manage.py db init
This will create all the folders required for migrations in your project folder.
Now we need to perform migrate operation ( its like staging or commiting before final changes)
$ python manage.py db migrate
To make the final changes to the database structure
$ python manage.py db upgrade
This will create all the necessary tables within your db
Feedly