sqlturk 0.9.1

Database schema migration tool that works in SQL

Overview

This tool helps you to keep track and evolve your database schema (SQL).

It works like this. Whenever you make changes to the database schema you put them into a “migration” - simply an .sql file with a sequence of SQL statements. Sqlturk keeps track of which migrations have been applied and runs them in a guaranteed order.

Design

There are plenty of tools to approach the problem of database schema migration. Here is how sqlturk is different:

• one-way migrations. There is no way to “rollback” a migration. In my experience, “downgrade” scripts are almost never used yet writing them adds considerable burden onto the developer. Their presense may add a false sense of security – since they used so rarely there is a big chance they will not work properly anyway.

• Python-agnostic. Sqlturk operates in terms of SQL DDL. It does not work in terms of SQLAlchemy ORM models or Django’s and thus it can be used in a much wider context. Plain SQL also means that a competent DBA who knows nothing about Python can author these scripts. Or they could be generated automatically by another tool.

• no magic. I wanted a tool that works in an obvious, easy-to-understand way. Changing database schema can have big consequences so it is important to be able to see what’s going on.

Not convinced? A couple of more sophisticated tools: Django South and sqlalchemy-migrate.

API usage

Short example:

>>> from sqlturk.migration import MigrationTool
>>> tool = MigrationTool('sqlite:///:memory:', migration_dir='testmigrations')
>>> tool.install() # create a database table to track schema changes
>>> tool.find_migrations()
['1_foobar', '2_foobar_data', '10_foobar_delete']
>>> tool.run_migrations()
>>> tool.find_migrations() # check that all migrations have been applied
[]

Example migration scripts can be found in the sqlturk’ source. Sqlturk uses SQLAlchemy syntax to specify database connection string, see its documentation for details.