Flask's Flask-migrate Database migration

Flask-migrate is an extension module of flask, which mainly extends the structure of database tables.

Official Document: http://flask-migrate.readthedocs.io/en/latest/

Use flask-migrate need to rely on flask-script components, see my other blog--Flask-script detailed

Installation

Pip Install Flask-migrate

Creating commands with examples

From flask import flaskfrom flask_sqlalchemy import sqlalchemyfrom flask_script import managerfrom flask_migrate import Mi Grate, Migratecommandapp = Flask (__name__) app.config[' sqlalchemy_database_uri '] = ' sqlite:///app.db ' db = SQLALCHEMY ( APP) Migrate = Migrate (app, db) Manager = Manager (APP) Manager.add_command (' db ', Migratecommand) class User (db). Model):    ID = db. Column (db. Integer, primary_key=true)    name = db. Column (db. String (*)) if __name__ = = ' __main__ ':    manager.run ()

Execute command

$ python manage.py db init   initializes the database, creates a Migations folder, and generates a Alembic_version table in the database $ Python manage.py db migrate  Create migration History $ python manage.py db upgrade  update database

Pit 1. Default values for fields when designing tables

operator = db. Column (db. String (nullable=true), server_default= "Init_data")

Here is the parameter Server_default instead of the default

2. If you report this error

Heroku Postgres, db migrate Fail:alembic.util.exc.CommandError:Can ' t locate revision identified by

Delete the data from the Alembic_version table

Flask's Flask-migrate Database migration