Hi, Stephen Thank you so so much for your help. That's very helpful. I'm trying to do this following https://docs.openstack.org/nova/latest/reference/database-migrations.html. Best wishes, Han Stephen Finucane <stephenfin@redhat.com> 于2022年5月25日周三 17:32写道：

On Sun, 2022-05-22 at 17:27 +0800, 韩光宇 wrote:

...

Hi,

I'm a beginner in OpenStack development.

I would like to try modifying by adding a property to the 'Instances' database table. But I didn't find description in the documentation of the data model mechanism and how to extend the database. https://docs.openstack.org/nova/latest/

Now, I know that it involves versined object model and alembic.

My question is: What is the process of adding a column to a table in the database?

Could someone show me the process of modifying a database table or recommend me the relevant documentation

Best wishes, Han

This is pretty well documented:

https://docs.openstack.org/nova/latest/reference/database-migrations.html

The tl;dr: is a) make your changes to 'nova/db/{main|api}/models.py' then (b) either auto-generate a schema using alembic's autogeneration functionality or write one yourself. We have tests in place that will ensure the migrations and models don't diverge.

You should know that making changes to the database schema will generally require a spec. You can find information on the purpose of specs and how to write one here:

https://specs.openstack.org/openstack/nova-specs/readme.html

Be careful not to treat this as a downstream-only thing (i.e. by forking nova). If you do, you are likely to cause yourself a lot of pain in the future as the database schema of upstream nova will invariably diverge.

If you have any questions, please ask here or (better) on #openstack-nova on OFTC IRC.

Hope this helps, Stephen