* cardinality of the array. Maybe there are a million entires, but only 3 distinct values. keeping an unsorted set of distinct values might, in this case, be a

* cardinality of the array. Maybe there are a million entires, but only 3 distinct values. keeping an unsorted set of distinct values might, in this case, be a much better solution that a sorted index. No mention was made of data cardinality.