AWS documentdb documentation change

Service: documentdb · 2026-03-31 · Documentation low

File: documentdb/latest/developerguide/arrayElemAt.md

Summary

Added comprehensive documentation for the $arrayElemAt operator in Amazon DocumentDB, including syntax, parameters, MongoDB shell examples, and code examples in Node.js and Python

Security assessment

This change adds standard documentation for a database operator function. The code examples include TLS connection parameters (tls=true, tlsCAFile) which are security best practices for DocumentDB connections, but these are standard configurations already documented elsewhere. There is no evidence this addresses a specific security vulnerability or incident.

Diff

diff --git a/documentdb/latest/developerguide/arrayElemAt.md b/documentdb/latest/developerguide/arrayElemAt.md
index 8b1378917..697624b7c 100644
--- a//documentdb/latest/developerguide/arrayElemAt.md
+++ b//documentdb/latest/developerguide/arrayElemAt.md
@@ -0,0 +1 @@
+[](/pdfs/documentdb/latest/developerguide/developerguide.pdf#arrayElemAt "Open PDF")
@@ -1,0 +3,124 @@
+[Documentation](/index.html)[Amazon DocumentDB](/documentdb/index.html)[Developer Guide](what-is.html)
+
+Example (MongoDB Shell)Code examples
+
+# $arrayElemAt
+
+The `$arrayElemAt` operator in Amazon DocumentDB allows you to retrieve an element from an array by its index position. This is particularly useful when you need to access a specific element within an array field in your documents.
+
+**Parameters**
+
+  * `array`: The input array from which an element is to be retrieved.
+
+  * `index`: The zero-based index position of the element to retrieve. This value must be a non-negative integer.
+
+
+
+
+## Example (MongoDB Shell)
+
+In this example, we'll demonstrate how to use the `$arrayElemAt` operator to retrieve specific elements from the `flight_miles` array in the `miles` collection.
+
+**Create sample documents**
+    
+    
+    db.miles.insertMany([
+      { "_id" : 1, "member_since" : ISODate("1987-01-01T00:00:00Z"), "credit_card" : false, "flight_miles" : [ 1205, 2560, 880 ]},
+      { "_id" : 2, "member_since" : ISODate("1982-01-01T00:00:00Z"), "credit_card" : true, "flight_miles" : [ 1205, 2560, 890, 2780 ]},
+      { "_id" : 3, "member_since" : ISODate("1999-01-01T00:00:00Z"), "credit_card" : true, "flight_miles" : [ 1205, 880 ]}
+    ]);
+
+**Query example**
+    
+    
+    db.miles.aggregate([
+      { $project: {
+        "_id": 1,
+        "first_mile": { $arrayElemAt: [ "$flight_miles", 0 ] },
+        "last_mile": { $arrayElemAt: [ "$flight_miles", -1 ] }
+      }}
+    ]);
+
+**Output**
+    
+    
+    { "_id" : 1, "first_mile" : 1205, "last_mile" : 880 }
+    { "_id" : 2, "first_mile" : 1205, "last_mile" : 2780 }
+    { "_id" : 3, "first_mile" : 1205, "last_mile" : 880 }
+
+In this example, we use the `$arrayElemAt` operator to retrieve the first and last elements of the `flight_miles` array for each document.
+
+## Code examples
+
+To view a code example for using the `$arrayElemAt` 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('miles');
+    
+      const result = await collection.aggregate([
+        { $project: {
+          "_id": 1,
+          "first_mile": { $arrayElemAt: [ "$flight_miles", 0 ] },
+          "last_mile": { $arrayElemAt: [ "$flight_miles", -1 ] }
+        }}
+      ]).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.mydatabase
+        collection = db.miles
+    
+        result = list(collection.aggregate([
+            { "$project": {
+                "_id": 1,
+                "first_mile": { "$arrayElemAt": [ "$flight_miles", 0 ] },
+                "last_mile": { "$arrayElemAt": [ "$flight_miles", -1 ] }
+            }}
+        ]))
+    
+        print(result)
+        client.close()
+    
+    example()
+
+![Warning](https://d1ge0kk1l5kms0.cloudfront.net/images/G/01/webservices/console/warning.png) **Javascript is disabled or is unavailable in your browser.**
+
+To use the Amazon Web Services Documentation, Javascript must be enabled. Please refer to your browser's Help pages for instructions.
+
+[Document Conventions](/general/latest/gr/docconventions.html)
+
+$anyElementTrue
+
+$arrayToObject
+
+Did this page help you? - Yes
+
+Thanks for letting us know we're doing a good job!
+
+If you've got a moment, please tell us what we did right so we can do more of it.
+
+Did this page help you? - No
+
+Thanks for letting us know this page needs work. We're sorry we let you down.
+
+If you've got a moment, please tell us how we can make the documentation better.