Question

Point out the correct statement.

(a) In MongoDB 3.0, cursor.explain() returns the indexOnly field to indicate whether the index covered a query

(b) When an index covers a query, MongoDB can both match the query conditions and return the results using only the index keys

(c) For read-heavy applications, deploy sharding and add one or more shards to a sharded cluster to distribute load among mongod instances

(d) All of the mentioned

I had been asked this question by my school teacher while I was bunking the class.

Query is from MongoDB Maintenance in section GridFS, BSON Datatype and Administration Concepts of MongoDB

Answer 1

The correct option is (b) When an index covers a query, MongoDB can both match the query conditions and return the results using only the index keys

Best explanation: MongoDB does not need to examine documents from the collection to return the results.