[mceachen]

Absolutely! The author was very thorough with the change process, which is great, but downtime during ALTER should absolutely be broached as well.

A staging system with a db server provisioned similarly to production lets you "smoke test" the migrations and deploy before you take down prod -- but especially with MySQL, that happily blocks all reads during an ALTER, you should really watch out for any table ~> 1M rows (or if they're wide, even fewer than that).

[glenngillen]

If you're using postgres on Heroku you can get a fork of your production db to test things like these:

http://devcenter.heroku.com/articles/heroku-postgresql#fork_...