The fastest sorts are the ones that do the least. If you can tolerate wrong answers, you can get higher throughput. That's a general maxim , which we'll be repeating in other contexts (for example, see Chapter 15, "Locks"). You can compensate for deficiencies that your DBMS may have and it is sometimes possible to use the side effects of other clauses to ease ORDER BY's job. So sorts don't have to be a worrisome thing.