That's not how postgres works. You're talking about 2PL. Serializable isolation level in postgres does have something called predicate locks, but those are actually quite a different thing.
No I was talking exactly about Predicate Locking.
They detect writes which conflict with earlier reads I dont think this could be called 2PL because it's only used to detect conflict.
Correctness requires that any insert into an index generate a rw-conflict with a concurrent serializable transaction if, after that insert, re-execution of any index scan of the other transaction would access the heap for a row not accessed during the previous execution.
