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Deprecated since v3.2

Starting in v3.2, the $returnKey operator is deprecated in mongosh. In mongosh, use cursor.returnKey() instead.

Only return the index field or fields for the results of the query. If $returnKey is set to true and the query does not use an index to perform the read operation, the returned documents will not contain any fields. Use one of the following forms:

db.collection.find( { <query> } )._addSpecial( "$returnKey", true )
db.collection.find( { $query: { <query> }, $returnKey: true } )
←  $query$showDiskLoc →
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