classCreateRailsAdminHistoriesTable<ActiveRecord::Migrationdefself.upcreate_table:rails_admin_historiesdo|t|t.text:message# title, name, or object_idt.string:usernamet.integer:itemt.string:tablet.integer:month,:limit=>2t.integer:year,:limit=>5t.timestampsendadd_index(:rails_admin_histories,[:item,:table,:month,:year],:name=>'index_rails_admin_histories')enddefself.downdrop_table:rails_admin_historiesendend