Thanks for the update, I think this will come in handy for lots of
folks.
- C
On Wed, 2010-12-22 at 21:05 -0800, Daniel Holth wrote:
> I am interested in supporting multiple packages that depend on each
> other's tables as a directed acyclic graph and do not import a common
> declarative base. To support that goal I've been working on
> stucco_evolution. stucco_evolution is an extension of repoze.evolution
> that works with SQLAlchemy.
>
>
> This is the design. Let me know if this would be useful to you.
>
>
> Packages that support stucco_evolution must contain a package named
> evolve. evolve/__init__.py contains some metadata, evolve/create.py
> creates all the tables for the latest version of the schema, and
> evolve/evolveN.py does the work necessary to upgrade the schema to
> version N from version N-1.
>
>
> Given a package name, stucco_evolution will try to import the evolve
> package inside that package and the evolve package from all its
> dependencies. stucco_evolution will return a topologically sorted list
> of these modules and evolution managers for each of these modules.
>
>
> By calling create() on each manager from the list in order, tables
> should be created in database-acceptable order.
>
>
> By calling repoze_evolution.evolve_to_latest(manager) with each
> manager from the list, all the schemas are brought up to the latest
> version. If this fails you will probably have a bad day.
>
>
> To upgrade your package to work with stucco_evolution, you would just
> add a packagename/evolve directory, add a couple of scripts (not
> evolve1.py until you have your first upgrade), and call
>
>
> session.begin()
> create_many(build_managers(session, find_dependencies('packagename')))
> # create all tables for packagename and dependencies
> session.commit()
>
>
> The implementation is at https://bitbucket.org/dholth/stucco_evolution
>
>
> stucco_evolution purposefully does not know anything about SQL, but
> there's nothing to stop you from using a DDL abstraction library in an
> evolveN script.
>
>
> __init__.py:
> NAME = 'a name'
> VERSION = 1 # an integer. start at 0 with no evolveN scripts.
> DEPENDS = ['stucco_evolution'] # a list containing 'stucco_evolution'
> except in stucco_evolution itself.
>
>
> create.py:
> def create(session):
> import mypackage
> mypackage.Base.metadata.create_all(session.bind)
>
>
> evolve1.py:
> def evolve(session):
> session.execute("ALTER TABLE foo ADD COLUMN baz INTEGER")
>
>
>
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