class DeleteEventsWithoutUser < ActiveRecord::Migration def up # User deletion without all the proper dependent: :destroy options might have left # Events without a submitter (event_user association is deleted, but Event itslef is not) Event.all.each do |event| if event.users.blank? event.destroy end end end def down raise ActiveRecord::IrreversibleMigration, 'Cannot reverse migration. Events deleted cannot be re-created' end end