[anarazel]

> It's not the default (read committed is) and I never saw serializable being set in actual production systems.

It's not the common mode of deployment, but it's definitely in prod use.

> You can do it, but then you have to be able to retry all of your transactions, including read.

Pure read transactions shouldn't need to be retried in postgres due to serialization errors. You need to have read-write dependencies for that.

That's not to say that effectively read only transactions aren't affected by serializable, you do need to record the necessary metadata for the serialization logic to work.

FWIW, if you know your transaction is read only and long running, you can start a transaction with START TRANSACTION READ ONLY DEFERRABLE, which makes the start transaction slower, but then does not need to do any work related to serializable while the transaction is running.