The following page refers to the aggregation stage $unset. For the update operator $unset, see $unset.
$unset
Removes/excludes fields from documents.
The $unset stage has the following syntax:
To remove a single field, the $unset takes a string that specifies the field to remove:
To remove multiple fields, the $unset takes an array of fields to remove.
{ $unset: [ "<field1>", "<field2>", ... ] }The $unset is an alias for the $project stage that removes/excludes fields:
{ $project: { "<field1>": 0, "<field2>": 0, ... } }To remove/exclude a field or fields within an embedded document, you can use the dot notation, as in:
{ $unset: "<field.nestedfield>" }or
{ $unset: [ "<field1.nestedfield>", ...] }Create a sample books collection with the following documents:
db.books.insertMany([ { "_id" : 1, title: "Antelope Antics", isbn: "0001122223334", author: { last:"An", first: "Auntie" }, copies: [ { warehouse: "A", qty: 5 }, { warehouse: "B", qty: 15 } ] }, { "_id" : 2, title: "Bees Babble", isbn: "999999999333", author: { last:"Bumble", first: "Bee" }, copies: [ { warehouse: "A", qty: 2 }, { warehouse: "B", qty: 5 } ] }])The following example removes the top-level field copies:
db.books.aggregate([ { $unset: "copies" } ])Alternatively, you can also use the following syntax:
db.books.aggregate([ { $unset: [ "copies" ] } ])Either operation returns the following documents:
{ "_id" : 1, "title" : "Antelope Antics", "isbn" : "0001122223334", "author" : { "last" : "An", "first" : "Auntie" } }{ "_id" : 2, "title" : "Bees Babble", "isbn" : "999999999333", "author" : { "last" : "Bumble", "first" : "Bee" } }The following example removes the top-level fields isbn and copies:
db.books.aggregate([ { $unset: [ "isbn", "copies" ] }])The $unset operation outputs the following documents:
{ "_id" : 1, "title" : "Antelope Antics", "author" : { "last" : "An", "first" : "Auntie" } }{ "_id" : 2, "title" : "Bees Babble", "author" : { "last" : "Bumble", "first" : "Bee" } }The following example removes the top-level field isbn, the embedded field first (from the name document) and the embedded field warehouse (from the elements in the copies array):
db.books.aggregate([ { $unset: [ "isbn", "author.first", "copies.warehouse" ] }])The $unset operation outputs the following documents:
{ "_id" : 1, "title" : "Antelope Antics", "author" : { "last" : "An" }, "copies" : [ { "qty" : 5 }, { "qty" : 15 } ] }{ "_id" : 2, "title" : "Bees Babble", "author" : { "last" : "Bumble" }, "copies" : [ { "qty" : 2 }, { "qty" : 5 } ] }The Node.js examples on this page use the sample_mflix database from the Atlas sample datasets. To learn how to create a free MongoDB Atlas cluster and load the sample datasets, see Get Started in the MongoDB Node.js driver documentation.
To use the MongoDB Node.js driver to add a $unset stage to an aggregation pipeline, use the $unset operator in a pipeline object.
The following example creates a pipeline stage that excludes the tomatoes field and the imdb.votes embedded field from return documents. The example then runs the aggregation pipeline:
const pipeline = [{ $unset: ["imdb.votes", "tomatoes"] }];const cursor = collection.aggregate(pipeline);return cursor;RetroSearch is an open source project built by @garambo | Open a GitHub Issue
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