ALTER TABLE `message_notifications` ADD COLUMN `priority` varchar(16) DEFAULT 'normal' NOT NULL;
ALTER TABLE `message_notifications` ADD COLUMN `is_archived` boolean DEFAULT false NOT NULL;
CREATE INDEX `message_notifications_priority_idx` ON `message_notifications`(`priority`);
CREATE INDEX `message_notifications_user_archived_idx` ON `message_notifications`(`user_id`, `is_archived`);