ALTER TABLE `sync_change`
  ADD COLUMN `processing_status` VARCHAR(20) NOT NULL DEFAULT 'pending' AFTER `after_snapshot`,
  ADD COLUMN `processing_notes` TEXT NULL AFTER `processing_status`,
  ADD COLUMN `processed_by` INT NULL AFTER `processing_notes`,
  ADD COLUMN `processed_at` DATETIME(3) NULL AFTER `processed_by`;

CREATE INDEX `sync_change_processing_status_created_at_idx`
  ON `sync_change`(`processing_status`, `created_at`);

CREATE INDEX `sync_change_processed_by_idx`
  ON `sync_change`(`processed_by`);

ALTER TABLE `sync_change`
  ADD CONSTRAINT `sync_change_processed_by_fkey`
    FOREIGN KEY (`processed_by`) REFERENCES `user`(`id`)
    ON DELETE SET NULL
    ON UPDATE CASCADE;