Services or capabilities described in AWS documentation might vary by Region. To see the differences applicable to the AWS European Sovereign Cloud Region, see the AWS European Sovereign Cloud User Guide.$rand
New from version 8.0
The $rand operator in Amazon DocumentDB is used to generate a random number between 0 and 1.
Parameters
None
Example (MongoDB Shell)
The following example demonstrates how to use the $rand operator to randomly select two documents from the temp collection.
Create sample documents
db.items.insertMany([
{ "name": "pencil", "quantity": 110 },
{ "name": "pen", "quantity": 159 }
])
Query example
db.items.aggregate([
{
$project: {
randomValue: { $rand: {} }
}
}
])
Output
[
{
_id: ObjectId('6924a5edd66dcae121d29517'),
randomValue: 0.8615243955294392
},
{
_id: ObjectId('6924a5edd66dcae121d29518'),
randomValue: 0.22815483022099903
}
]
Code examples
To view a code example for using the $rand 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('items');
const result = await collection.aggregate([
{
$project: {
randomValue: { $rand: {} }
}
}
]).toArray();
console.log(result);
await client.close();
}
example();
- Python
-
from pymongo import MongoClient
def example():
client = MongoClient('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false')
db = client['test']
collection = db['items']
result = list(collection.aggregate([
{
"$project": {
"randomValue": { "$rand": {} }
}
}
]))
print(result)
client.close()
example()