class UpdateUsersCaseInsensitiveEmails < ActiveRecord::Migration[4.2] def up execute "DROP INDEX index_users_on_email" # Find duplicate emails. results = execute <<SQL SELECT id, email, count FROM (SELECT id, email, row_number() OVER(PARTITION BY lower(email) ORDER BY id asc) AS count FROM users) dups WHERE dups.count > 1 SQL results.each do |row| execute "UPDATE users SET email = '#{row['email'].downcase}#{row['count']}' WHERE id = #{row['id']}" end execute "UPDATE users SET email = lower(email)" execute "CREATE UNIQUE INDEX index_users_on_email ON users ((lower(email)));" end def down execute "DROP INDEX index_users_on_email" execute "CREATE UNIQUE INDEX index_users_on_email ON users (email);" end end