cursor.returnKey()
This page documents a mongosh method. This is not the documentation for a language-specific driver, such as Node.js.
For MongoDB API drivers, refer to the language-specific MongoDB driver documentation.
Modifies the cursor to return index keys rather than the documents.
The cursor.returnKey() has the following form:
returnKey() is attached to with a modified result set. This allows for additional cursor modifiers to be chained.
This method is available in deployments hosted in the following environments:
MongoDB Atlas: The fully managed service for MongoDB deployments in the cloud
This command is supported in all MongoDB Atlas clusters. For information on Atlas support for all commands, see Unsupported Commands.
MongoDB Enterprise: The subscription-based, self-managed version of MongoDB
MongoDB Community: The source-available, free-to-use, and self-managed version of MongoDB
If the query does not use an index to perform the read operation, the cursor returns empty documents.
The restaurants collection contains documents with the following schema:
db.restaurants.insertOne( { _id: ObjectId("564f3a35b385149fc7e3fab9"), address: { building: "2780", coord: [ -73.98241999999999, 40.579505 ], street: "Stillwell Avenue", zipcode: "11224" }, borough: "Brooklyn", cuisine: "American ", grades: [ { date: ISODate("2014-06-10T00:00:00Z"), grade: "A", score: 5 }, { date: ISODate("2013-06-05T00:00:00Z"), grade: "A", score: 7 } ], name: "Riviera Caterer", restaurant_id: "40356018" })The collection has two indexes in addition to the default _id index:
{ "v" : 1, "key" : { "_id" : 1 }, "name" : "_id_", "ns" : "guidebook.restaurant"},{ "v" : 1, "key" : { "cuisine" : 1 }, "name" : "cuisine_1", "ns" : "guidebook.restaurant"},{ "v" : 1, "key" : { "_fts" : "text", "_ftsx" : 1 }, "name" : "name_text", "ns" : "guidebook.restaurant", "weights" : { "name" : 1 }, "default_language" : "english", "language_override" : "language", "textIndexVersion" : 3}The following code uses the cursor.returnKey() method to return only the indexed fields used for executing the query:
var csr = db.restaurant.find( { "cuisine" : "Japanese" } )csr.returnKey()This returns the following:
{ "cuisine" : "Japanese" }{ "cuisine" : "Japanese" }{ "cuisine" : "Japanese" }{ "cuisine" : "Japanese" }...RetroSearch is an open source project built by @garambo | Open a GitHub Issue
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