class FixInvalidMysqlIndices < ActiveRecord::Migration def up if index_exists?("settings", ["target_type", "target_id", "var"]) remove_index "settings", ["target_type", "target_id", "var"] add_index "settings", ["target_type", "target_id"], name: "index_settings_on_target_type_and_target_id", unique: true end end def down if index_exists?("settings", ["target_type", "target_id"]) remove_index "settings", ["target_type", "target_id"] add_index "settings", ["target_type", "target_id", "var"], name: "index_settings_on_target_type_and_target_id_and_var", unique: true end end end