AWS documentdb documentation change

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

File: documentdb/latest/developerguide/first.md

Summary

Added documentation for the $first aggregation operator in Amazon DocumentDB, including syntax, parameters, MongoDB shell examples, and code examples in Node.js and Python with connection strings.

Security assessment

This change documents a new aggregation operator ($first) available from version 5.0. The code examples include standard TLS connection parameters (tls=true, tlsCAFile) which are security best practices for DocumentDB connections, but this is not new security documentation - it's standard connection configuration that appears in many DocumentDB examples. There is no evidence this addresses a specific security vulnerability or incident.

Diff

diff --git a/documentdb/latest/developerguide/first.md b/documentdb/latest/developerguide/first.md
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--- a//documentdb/latest/developerguide/first.md
+++ b//documentdb/latest/developerguide/first.md
@@ -0,0 +1 @@
+[](/pdfs/documentdb/latest/developerguide/developerguide.pdf#first "Open PDF")
@@ -1,0 +3,136 @@
+[Documentation](/index.html)[Amazon DocumentDB](/documentdb/index.html)[Developer Guide](what-is.html)
+
+Example (MongoDB Shell)Code examples
+
+# $first
+
+New from version 5.0.
+
+Not supported by Elastic cluster.
+
+The `$first` operator in Amazon DocumentDB returns the first document from a grouped set of documents. It is commonly used in aggregation pipelines to retrieve the first document that matches a specific condition.
+
+**Parameters**
+
+  * `expression`: The expression to return as the first value in each group.
+
+
+
+
+## Example (MongoDB Shell)
+
+The following example demonstrates the use of the `$first` operator to retrieve the first item value encountered for each category during the aggregation.
+
+Note: `$first` returns the first document based on the current order of documents in the pipeline. To ensure a specific order (e.g., by date, price, etc.), a `$sort` stage should be used before the `$group` stage.
+
+**Create sample documents**
+    
+    
+    db.products.insertMany([
+      { _id: 1, item: "abc", price: 10, category: "food" },
+      { _id: 2, item: "jkl", price: 20, category: "food" },
+      { _id: 3, item: "xyz", price: 5, category: "toy" },
+      { _id: 4, item: "abc", price: 5, category: "toy" }
+    ]);
+
+**Query example**
+    
+    
+    db.products.aggregate([
+      { $group: { _id: "$category", firstItem: { $first: "$item" } } }
+    ]);
+
+**Output**
+    
+    
+    [
+      { "_id" : "food", "firstItem" : "abc" },
+      { "_id" : "toy", "firstItem" : "xyz" }
+    ]
+
+## Code examples
+
+To view a code example for using the `$first` command, choose the tab for the language that you want to use:
+
+Node.js
+    
+    
+    
+    const { MongoClient } = require('mongodb');
+    
+    async function example() {
+      const uri = 'mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false';
+      const client = new MongoClient(uri);
+    
+      try {
+        await client.connect();
+    
+        const db = client.db('test');
+        const collection = db.collection('products');
+    
+        const result = await collection.aggregate([
+          { $group: { _id: "$category", firstItem: { $first: "$item" } } }
+        ]).toArray();
+    
+        console.log(result);
+    
+      } catch (error) {
+        console.error('Error:', error);
+      } finally {
+        await client.close();
+      }
+    }
+    
+    example();
+
+Python
+    
+    
+    
+    from pymongo import MongoClient
+    from pprint import pprint
+    
+    def example():
+        client = None
+        try:
+            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['products']
+    
+            result = list(collection.aggregate([
+                { '$group': { '_id': '$category', 'firstItem': { '$first': '$item' } } }
+            ]))
+    
+            pprint(result)
+    
+        except Exception as e:
+            print(f"An error occurred: {e}")
+    
+        finally:
+            if client:
+                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)
+
+$filter
+
+$floor
+
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+
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+
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