I understand scenarios where COLLSCAN s preferred, which include large range match, return majority of requirements etc.
But, I have applied find with exact match on a collection , which do not have any index apart from _id. In absence of index, COLLSCAN obvious. But, my question is how come execution time of exact match using COLLSCAN and IXSCAN would be almost same?
Test collection : emp (_id, name , salary)
Test Query : db.emp.find(salary = )