IDM 3.5.1

I need to find a user, I can query by Employee ID (a custom CIS attr,
ya, we should have used workforceID but I just work here..)

Or I can query by users who have a DN syntax attr, set to a specific DN.

Which is the more efficient query? DN is a 32 bit INT ultimatly in its
DB storage. A CIS attr is potentailly a harder match, except that it is
indexed, (the DN is not) and ALL values are the same format (E or V,
then 6 ints).

I can search either way, but I would prefer to use the more efficient
search if possible.

(Not sure how to test the efficiency, short of looping it thousands of
times, timing it, and then doing it the other way... Then comparing
times.)