Open Stack

----- Original Message -----
> From: "Sean Dague" <sdague at linux.vnet.ibm.com>
> To: openstack at lists.launchpad.net
> Sent: Friday, April 27, 2012 10:21:17 AM
> Subject: Re: [Openstack] database migration cleanup
> 
> On 04/26/2012 03:24 PM, Dan Prince wrote:
> <snip>
> > I think this scheme would support users who follow stable releases
> > as well as users who follow trunk very closely.
> >
> > We talked about this at the conference but I thought this issue
> > might be near and dear to some of our end users so it was worth
> > discussing on the list.
> >
> > What are general thoughts on this approach?
> 
> Is there any support in sqlalchemy, or related tools, to handle
> migrations the way rails does, where a schema file is created at the
> end
> of every migration? It would be ideal if we both had a full migration
> history, as well as a short cut at any snap shot to get to the end.

Ah. Yes, the Rails schema.rb. I looked around for just this sort of thing and didn't find much. Python-migrate has some "experimental" support for generating models and I did make use of that initially. See 'create_model' below:


[root at nova1 migrate_repo]# python ./manage.py --repository=./ --url=mysql://nova:password@localhost/nova
Usage: manage.py COMMAND ...

    Available commands:
        compare_model_to_db          - compare MetaData against the current database state
	create                       - create an empty repository at the specified path
	create_model                 - dump the current database as a Python model to stdout
	db_version                   - show the current version of the repository under version control
	downgrade                    - downgrade a database to an earlier version
	drop_version_control         - removes version control from a database
	help                         - displays help on a given command
	make_update_script_for_model - create a script changing the old MetaData to the new (current) MetaData
	manage                       - creates a Python script that runs Migrate with a set of default values
	script                       - create an empty change Python script
	script_sql                   - create empty change SQL scripts for given database
	source                       - display the Python code for a particular version in this repository
	test                         - performs the upgrade and downgrade command on the given database
	update_db_from_model         - modify the database to match the structure of the current MetaData
	upgrade                      - upgrade a database to a later version
	version                      - display the latest version available in a repository
	version_control              - mark a database as under this repository's version control

----

python-migrate's 'create_model' does not however give you something that exactly matches the schema you'd get by running the all the migrations. So auto generation doesn't appear to be an option right now. It would be nice to contribute python-migrate in this regard and get better support for model generation, etc. Maybe a good long term goal?

Dan


> 
> 	-Sean
> 
> --
> Sean Dague
> IBM Linux Technology Center
> email: sldague at us.ibm.com
> alt-email: sdague at linux.vnet.ibm.com
> 
> 
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