DO $$
BEGIN
    IF EXISTS (
        SELECT 1
        FROM source_connections
        WHERE source_type = 'manual'
    ) THEN
        RAISE EXCEPTION 'cannot downgrade while manual source connections exist';
    END IF;
END
$$;

ALTER TABLE source_connections
    DROP CONSTRAINT IF EXISTS source_connections_source_type_check;

ALTER TABLE source_connections
    ADD CONSTRAINT source_connections_source_type_check
    CHECK (source_type IN ('pp', 'alist', 'dingtalk'));