You are not[1]. This is not a complex problem but the author has managed to make a blog article out of it and come to the conclusion that rational numbers are required.

The reason the author gives for rejecting your proposal is they have added a uniqueness constraint which makes the update awkward but you can indeed work around that in a variety of ways or just drop the uniqueness constraint altogether.

[1] Although update doesn't have an "order by" clause[2] but I'm assuming you mean 'update' and then subsequently 'select' with the order by. I think if you actually want an update to proceed sequentially in some order you have to use a cursor.

[2] Author is using postgres so this would be the relevant doc https://www.postgresql.org/docs/current/sql-update.html

You are effectively updating many todos. The benefit of the solution presented by the author is not about performance, but rather minimizing change.

Imagine a situation when multiple clients keep copies of todos and rely on optimistic locking for updates.

This is a cool little problem brilliantly solved.

It works in MariaDB.