$toString - Amazon DocumentDB
Example (MongoDB Shell)Code examples

$toString

New from version 4.0

The $toString operator in Amazon DocumentDB is used to convert a value of any type (except for null) to a string representation. This can be useful when you need to perform string operations on values that are not originally in string format.

Parameters

  • expression: The expression to convert to a string.

Example (MongoDB Shell)

The following example demonstrates how to use the $toString operator to convert numeric values to strings.

Create sample documents

db.numbers.insertMany([
  { "_id": 1, "value": 42 },
  { "_id": 2, "value": 3.14 }
]);

Query example

db.numbers.aggregate([
  { $project: {
    _id: 1,
    valueAsString: { $toString: "$value" }
  }}
]);

Output

{ "_id": 1, "valueAsString": "42" }
{ "_id": 2, "valueAsString": "3.14" }

Code examples

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

Node.js
const { MongoClient } = require('mongodb');

async function example() {
  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('numbers');

  const result = await collection.aggregate([
    { $project: {
      _id: 1,
      valueAsString: { $toString: '$value' }
    }}
  ]).toArray();

  console.log(result);
  client.close();
}

example();
Python
from pymongo import MongoClient

def example():
    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['numbers']

    result = list(collection.aggregate([
        { '$project': {
            '_id': 1,
            'valueAsString': { '$toString': '$value' }
        }}
    ]))

    print(result)
    client.close()

example()