On 12/18/2013 2:11 PM, Dan Prince wrote:
----- Original Message -----
From: "Matt Riedemann" <[email protected]>
To: "OpenStack Development Mailing List (not for usage questions)"
<[email protected]>
Sent: Wednesday, December 18, 2013 12:27:49 PM
Subject: [openstack-dev] Adding DB migration items to the common review
checklist
I've seen this come up a few times in reviews and was thinking we should
put something in the general review checklist wiki for it [1].
Basically I have three things I'd like to have in the list for DB
migrations:
1. Unique constraints should be named. Different DB engines and
SQLAlchemy dialects automatically name the constraint their own way,
which can be troublesome for universal migrations. We should avoid this
by enforcing that UCs are named when they are created. This means not
using the unique=True arg in UniqueConstraint if the name arg isn't
provided.
2. Foreign keys should be named for the same reasons in #1.
3. Foreign keys shouldn't be created against nullable columns. Some DB
engines don't allow unique constraints over nullable columns and if you
can't create the unique constraint you can't create the foreign key, so
we should avoid this. If you need the FK, then the pre-req is to make
the target column non-nullable. Think of the instances.uuid column in
nova for example.
Unless anyone has a strong objection to this, I'll update the review
checklist wiki with these items.
No objection to these.
One possible addition would be to make sure that migrations stand on their own
as much as possible. Code sharing, while good in many cases, can bite you in DB
migrations because fixing a bug in the shared code may change the behavior of
an old (released) migration. So by sharing migration code it then can become
easier to break upgrades paths down the road. If we make some exceptions to
this rule with nova.db.sqlalchemy we need to be very careful that we don't
change the behavior in those functions. Automated tests help here too.
Dan
Not sure if this is pure coincidence, but case in point:
https://review.openstack.org/#/c/62965/
[1] https://wiki.openstack.org/wiki/ReviewChecklist
--
Thanks,
Matt Riedemann
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--
Thanks,
Matt Riedemann
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