1.

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 mentionedI 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»

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.



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