class AddIndexForShixunServices < ActiveRecord::Migration[5.2]
  def change
    sql = %Q(delete from shixun_service_configs where (shixun_id, mirror_repository_id) in
            (select * from (select shixun_id, mirror_repository_id from shixun_service_configs group by shixun_id, mirror_repository_id having count(*) > 1) a)
            and id not in (select * from (select min(id) from shixun_service_configs group by shixun_id, mirror_repository_id having count(*) > 1 order by id) b))
    ActiveRecord::Base.connection.execute sql
    add_index :shixun_service_configs, [:shixun_id, :mirror_repository_id], unique: true, name: "shixun_id_mirror_id_unique"
  end
end