Question

Point out the wrong statement.

(a) TTL index is ideal for certain types of information like machine generated event data, logs, and session information that only need to persist in a database for a finite amount of time

(b) You cannot combine the sparse index option with the unique index option

(c) TTL indexes are special indexes that MongoDB can use to automatically remove documents from a collection after a certain amount of time

(d) None of the mentioned

This question was posed to me by my college professor while I was bunking the class.

My doubt stems from Index Types in division Index/Indexing Concepts of MongoDB

Answer 1

Correct choice is (b) You cannot combine the sparse index option with the unique index option

To elaborate: You can combine to reject documents that have duplicate values for a field but ignore documents that do not have the indexed key.