Stupidly simple SQLalchemy model migration

This simple script pulls in the relavant database and model parameters from pylons .INI

It relies on the migrate egg for the diff and applyModel functions, and also makes use of the ConfigParser embedded in paste.deploy.loadwsgi.

It is most useful when rapidly developing / prototyping a Pylons application.

Installation of required modules

easy_install SQLAlchemy easy_install sqlalchemy-migrate

Setup of MYPROKJ .INI files and model meta files

1. Within the Pylons .INI file, it looks for a section called [app] (the typical value is [app:main])

2. The database URL is found from sqlalchemy.url :

   sqlalchemy.url = sqlite:///%(here)s/development.db

3. The metadata for SQLalchemy is taken from a new entry : migrate.metadata :

   migrate.metadata = MYPROJ.model.meta:metadata

Where the file MYPROJ/model/meta.py contains the following : :

from sqlalchemy import schema
metadata = schema.MetaData()

# The declarative DataBase base Object
Base = declarative_base(metadata=metadata)

Syntax

(python-local) $ python sqlalchemy-migrate-pylons.py --help

Usage: sqlalchemy-migrate-pylons.py [options] STANDALONE.ini

Options:

-h, --help show this help message and exit -a, --app section to parse in ini file (default=app:main) -c, --commit Use diffs to update database (default=False) -v, --verbose Show debug messages

Normal usage

1. To check what needs to be changed:

   python sqlalchemy-migrate-pylons.py development.ini

2. To implement the changes and report back:

   python sqlalchemy-migrate-pylons.py --commit development.ini

Known Issues

• Changing a model from nullable=True to nullable=False can be a problem, since the migrate package doesn't seem to understand default=''
• The script is dependent on sqlalchemy-migrate, so could be incorporated into that package
• OTOH, it would probably sit better as a Paster-Pylons plug-in
• Please let me know if there are any other problems.

As always : Back up your data before doing a migrate.