ALTER TABLE `payment_methods`
  ADD COLUMN IF NOT EXISTS `is_default` TINYINT(1) NOT NULL DEFAULT 0 AFTER `is_system`;

ALTER TABLE `payment_methods`
  ADD COLUMN IF NOT EXISTS `system_key` VARCHAR(64) NULL AFTER `is_default`;

SET @index_exists := (
  SELECT COUNT(1)
  FROM information_schema.statistics
  WHERE table_schema = DATABASE()
    AND table_name = 'payment_methods'
    AND index_name = 'uq_payment_methods_company_system_key'
);

SET @create_index_sql := IF(
  @index_exists = 0,
  'CREATE UNIQUE INDEX `uq_payment_methods_company_system_key` ON `payment_methods` (`company_id`, `system_key`)',
  'SELECT 1'
);

PREPARE stmt FROM @create_index_sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

UPDATE `payment_methods`
SET `is_default` = 0
WHERE `is_default` IS NULL;

UPDATE `payment_methods`
SET `system_key` = NULL
WHERE `is_system` = 0;