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The $hint operator forces the query optimizer to use a specific index to fulfill the query. Specify the index either by the index name or by document.

Use $hint for testing query performance and indexing strategies. The mongo shell provides a helper method hint() for the $hint operator.

Consider the following operation:

db.users.find().hint( { age: 1 } )

This operation returns all documents in the collection named users using the index on the age field.

You can also specify a hint using either of the following forms:

db.users.find()._addSpecial( "$hint", { age : 1 } )
db.users.find( { $query: {}, $hint: { age : 1 } } )


To combine $explain and $hint operations when $hint is part of the document, as in the following query statement:

db.users.find( { $query: {}, $hint: { age : 1 } } )

You must add the $explain option to the document, as in the following:

db.users.find( { $query: {}, $hint: { age : 1 }, $explain: 1 } )
←   $explain $maxScan  →