Python 3.7.3 : Using the flask - part 015.

In this tutorial, I will show you how to migrate using the Database Migrations in flask project.
Because my laptop is gone I use my old Linux.
First you need to install these python modules with --user argument for Linux:

[mythcat@desk my_flask]$ pip3 install flask-migrate --user
...
[mythcat@desk my_flask]$ pip3 install flask-script --user

Let's test this new issue with server.py file by adding these python modules:

#migrate 
from flask_script import Manager
from flask_migrate import Migrate, MigrateCommand
...
# create migrate object with db 
migrate = Migrate(app, db)
# create manager 
manager = Manager(app)
# create db command for manager 
manager.add_command('db', MigrateCommand)
...
# add new columns into database 
class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True)
    email = db.Column(db.String(120), unique=True)
    gender = db.Column(db.String(5), unique=True)
    work = db.Column(db.String(33), unique=True)
    city = db.Column(db.String(15), unique=True)
...
# the default name main
if __name__ == '__main__':
    manager.run()
    app.run(debug=True)

Let's fix this migrate issue with the new command:

[mythcat@desk my_flask]$ python3 server.py db init 
  Creating directory /home/mythcat/project_github/my_flask/migrations ... done
  Creating directory /home/mythcat/project_github/my_flask/migrations/versions ... done
  Generating /home/mythcat/project_github/my_flask/migrations/script.py.mako ... done
  Generating /home/mythcat/project_github/my_flask/migrations/env.py ... done
  Generating /home/mythcat/project_github/my_flask/migrations/alembic.ini ... done
  Generating /home/mythcat/project_github/my_flask/migrations/README ... done
  Please edit configuration/connection/logging settings in '/home/mythcat/project_github/my_flask/migrations
/alembic.ini'
  before proceeding.

[mythcat@desk my_flask]$ python3 server.py db migrate
INFO  [alembic.runtime.migration] Context impl SQLiteImpl.
INFO  [alembic.runtime.migration] Will assume non-transactional DDL.
INFO  [alembic.autogenerate.compare] Detected added column 'user.city'
INFO  [alembic.autogenerate.compare] Detected added column 'user.gender'
INFO  [alembic.autogenerate.compare] Detected added column 'user.work'
INFO  [alembic.autogenerate.compare] Detected added unique constraint 'None' on '['city']'
INFO  [alembic.autogenerate.compare] Detected added unique constraint 'None' on '['gender']'
INFO  [alembic.autogenerate.compare] Detected added unique constraint 'None' on '['work']'
  Generating /home/mythcat/project_github/my_flask/migrations/versions/ca70c42b5b7a_.py ... done

[mythcat@desk my_flask]$ python3 server.py db upgrade 
INFO  [alembic.runtime.migration] Context impl SQLiteImpl.
INFO  [alembic.runtime.migration] Will assume non-transactional DDL.
INFO  [alembic.runtime.migration] Running upgrade  -> ca70c42b5b7a, empty message
ERROR [root] Error: No support for ALTER of constraints in SQLite dialect

The database fiels is changed by this command.
Let's see with sqlite3 tool:

[mythcat@desk my_flask]$ sqlite3 server.sqlite 
SQLite version 3.26.0 2018-12-01 12:34:55
Enter ".help" for usage hints.
sqlite> .tables
alembic_version  user           
sqlite> .schema user
CREATE TABLE user (
        id INTEGER NOT NULL, 
        username VARCHAR(80), 
        email VARCHAR(120), city VARCHAR(15), gender VARCHAR(5), work VARCHAR(33), 
        PRIMARY KEY (id), 
        UNIQUE (username), 
        UNIQUE (email)
);

You can see my source code here.