db_migrate.py

# -*- coding: utf-8 -*-
import imp
from migrate.versioning import api
from app import db
from config import SQLALCHEMY_DATABASE_URI, SQLALCHEMY_MIGRATE_REPO

"""
The way SQLAlchemy-migrate creates a migration is by comparing the structure
of the database (obtained in our case from file app.db) against the structure
of our models (obtained from file app/models.py).
The differences between the two are recorded as a migration script inside
the migration repository
"""
v = api.db_version(SQLALCHEMY_DATABASE_URI, SQLALCHEMY_MIGRATE_REPO)
migration = SQLALCHEMY_MIGRATE_REPO + ('/versions/%03d_migration.py' % (v + 1))
tmp_module = imp.new_module('old_model')
old_model = api.create_model(SQLALCHEMY_DATABASE_URI, SQLALCHEMY_MIGRATE_REPO)
exec(old_model, tmp_module.__dict__)
script = api.make_update_script_for_model(SQLALCHEMY_DATABASE_URI,
                                            SQLALCHEMY_MIGRATE_REPO,
                                            tmp_module.meta, db.metadata)
open(migration, "wt").write(script)
api.upgrade(SQLALCHEMY_DATABASE_URI, SQLALCHEMY_MIGRATE_REPO)
v = api.db_version(SQLALCHEMY_DATABASE_URI, SQLALCHEMY_MIGRATE_REPO)
print('New migration saved as ' + migration)
print('Current database version: ' + str(v))