Just "using a transaction" is insufficient. You must be prepared to handle the case that neither the INSERT nor the UPDATE succeeds (with READ COMMITTED isolation), or that the transaction fails (with REPEATABLE READ isolation or better), by repeating the transaction. And if latency is at all a concern to you, you must wrap this all in a stored procedure to avoid the necessary round-trip-time between the commands.
Hence this is more than just saving typing a couple lines -- this saves writing entire stupid loops to do what is conceptually a simple (and very common) operation.
Hence this is more than just saving typing a couple lines -- this saves writing entire stupid loops to do what is conceptually a simple (and very common) operation.
Postgres gets better and better.