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Meant to be deleted

I love this idea for a custom rake task (rails db:migrate:archive) to occasionally archive past migration files.

# lib/tasks/migration_archive.rake
namespace :db do
  namespace :migrate do
    desc 'Archives old DB migration files'
    task :archive do
      sh 'mkdir -p db/migrate/archive'
      sh 'mv db/migrate/*.rb db/migrate/archive'
    end
  end
end

That way you still have access to them as development artifacts. Meanwhile you remove the migration clutter and communicate a reliance on the schema file for standing up fresh database instances (in dev/test/staging).

Data migrations

They don't go into much detail about data migrations. It's hard to prescribe a one-size-fits-all because sometimes the easiest thing to do is embed a bit of data manipulation in a standard schema migration, sometimes you want to manually run a SQL file against each database, or maybe you want to set up a process for these changes with a tool like the after_party gem.

Reversible migrations

For standard migrations, it is great to rely on the change method to ensure migrations are reversible. It's important to recognize what kinds of migrations are and aren't reversible. Sometimes we need to write some raw SQL and for that we are going to want up and down methods.