Services or capabilities described in Amazon Web Services documentation might vary by Region. To see the differences applicable to the China Regions, see Getting Started with Amazon Web Services in China (PDF).

$unset

The $unset operator in Amazon DocumentDB is used to remove a specified field from a document. When a field is removed using $unset, the field is deleted from the document, and the document size is reduced accordingly. This can be useful when you want to remove unnecessary data from your documents.

Parameters

Example (MongoDB Shell)

The following example demonstrates how to use the $unset operator to remove the Words field from a document in the example collection.

Create sample documents

db.example.insert({
    "DocName": "Document 1",
    "Date": {
        "Month": 4,
        "Day": 18,
        "Year": 1987,
        "DoW": "Saturday"
    },
    "Words": 2482
})

Query example

db.example.update(
    { "DocName" : "Document 1" },
    { $unset: { Words:1 } }
)

Output

{
    "DocName": "Document 1",
    "Date": {
        "Month": 4,
        "Day": 18,
        "Year": 1987,
        "DoW": "Saturday"
    }
}

In this example, the $unset operator is used to remove the Words field from the document with DocName equal to "Document 1". The resulting document no longer contains the Words field.

Code examples

To view a code example for using the $unset command, choose the tab for the language that you want to use:

Node.js

const { MongoClient } = require('mongodb');

async function removeField() {
  const client = await MongoClient.connect('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false');
  const db = client.db('test');
  const collection = db.collection('example');

  const result = await collection.updateOne(
    { "DocName": "Document 1" },
    { $unset: { "Words": 1 } }
  );

  console.log(`Modified ${result.modifiedCount} document(s)`);
  client.close();
}

removeField();

Python

from pymongo import MongoClient

def remove_field():
    client = MongoClient('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false')
    db = client['test']
    collection = db['example']

    result = collection.update_one(
        {"DocName": "Document 1"},
        {"$unset": {"Words": 1}}
    )

    print(f"Modified {result.modified_count} document(s)")
    client.close()

remove_field()