Migrating DATA - not just schema, Rails

Question

Sometimes, data migrations are required. As time passes, code changes and migrations using your domain model are no longer valid and migrations fail. What a

Answer 1

Best practice is: don't use models in migrations. Migrations change the way AR maps, so do not use them at all. Do it all with SQL. This way it will always work.

This:

User.all.each do |user|
  user.applied_at = user.partner_application_at
  user.save
end

I would do like this

update "UPDATE users SET applied_at=partner_application_at"