David Wall <d.wall@xxxxxxxxxxxx> writes: > ... So we're trying to determine > if there's actually any difference between commit/rollback after SELECT > statements (with rows returned or not), a bit like if there's any > difference for an UPDATE statement that returns zero rows were updated. They're different code paths, but I'd expect any performance difference to be at the noise level; if nothing happened in the transaction then no WAL traffic will be emitted in either case. A more useful thing to think about, IMO, is this: if your app thinks that the statement had no side-effects but actually it did (maybe it called a volatile function that did something), would you want those effects to be persisted or not? regards, tom lane
