However mostly it is. Consider the example with the ID's if he would have an index with all the fields he would need, example he would only need the id and the

However mostly it is. Consider the example with the ID's if he would have an index with all the fields he would need, example he would only need the id and the email he could create a index with them and the query would be faster, that would be a index only scan (https://wiki.postgresql.org/wiki/Index-only_scans https://wiki.postgresql.org/wiki/Index-only_scans)