Output columns in database schema order, not A-Z order. about annotate_models

[oskarpearson]

I've had problems with this in the past because, in reality, people run database migrations in different orders.

Let's say we have three developers working at the same time

Consider this timeline:

Monday

• Developer 1 creates and their a database migration in their branch. It adds column sometable.foo in migration 0001 to their local db.
• Developer 2 creates and runs a database migration in their branch. It adds column sometable.bar in migration 0002 to their local db.

Tuesday

• Developer 1 merges their code to production. Production table consists of [:id, :foo]
• Developer 2 rebases.
• Developer 2 runs db:migrate. Column foo gets added to their database table. Their table consists of [:id, :bar, :foo]
• Developer 2 submits a diff that changes the annotate order to db

Every time Developer 2 runs db:migrate and annotate runs, it'll show a 'diff' on developer 2, since their local table is out of order. The only way out of this is to db rollback, and then roll forwards, or reset their db entirely.

Why do this at all?

I'm not convinced there's a lot of value to trying to manage the order of columns in the database. Unless you have an exceptional situation, you're micro-optimising for very little benefit.

• You can't later insert a column between columns 1 and 2 without rebuilding the whole table. Which involves massive downtime for most db engines
• Most ID fields should be indexed, so the placement in the table doesn't matter very much anyway.