Question

Point out the wrong statement.

(a) If MongoDB can use an index scan to obtain the requested sort order, the result will not include a SORT stage

(b) In previous versions of MongoDB, cursor.explain() returned the scanAndOrder field to specify whether MongoDB could use the index order to return sorted results

(c) If MongoDB uses indexes for a $and expression, the result will include the AND stage with an inputStages array that details the replicata sets

(d) None of the mentioned

The question was posed to me in unit test.

My question comes from Optimization Strategies topic in section Monitoring MongoDB and Optimization Strategies for MongoDB of MongoDB

Answer 1

Right choice is (a) If MongoDB can use an index scan to obtain the requested sort order, the result will not include a SORT stage

Easiest explanation: If MongoDB uses indexes for a $or expression, the result will include the OR stage with an inputStages array that details the indexes