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(PDF).
$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()