class WarnAboutDuplicateUsernames < ActiveRecord::Migration def up names = User.group('LOWER(username)').having('count(*) > 1').pluck('LOWER(username)') if names.length > 0 puts "-----------------------------------------------------" puts "--------------------- WARNiNG -----------------------" puts "-------- Found users with duplicate usernames -------" puts "-----------------------------------------------------" puts "For the users to log in using their username they have to change it to a unique name" names.each do |name| puts puts "'#{name}' is used multiple times:" User.where(['LOWER(username) = ?', name]).each do |u| puts "#{u.id}\t#{u.email}" end end puts puts end end end