Other isolation levels will make the concurrent update find zero rows. Serializable gives an error instead which you reliable can retry the transaction on. The

Other isolation levels will make the concurrent update find zero rows. Serializable gives an error instead which you reliable can retry the transaction on. They fail in different ways (for serializable a in this case more useful way) which should have been pointed out by the author. It does not seem like he actually tested what isolation levels does or he tested it in a database which does not provide serializable isolation.