AWS documentdb documentation change

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

File: documentdb/latest/developerguide/substr.md

Summary

Added new documentation page for the $substr operator in Amazon DocumentDB, including parameter descriptions, MongoDB shell examples, and code examples in Node.js and Python

Security assessment

This change adds routine documentation for a database operator ($substr) with standard usage examples. There is no mention of security vulnerabilities, security fixes, or security features. The examples show typical database operations without any security context or warnings about potential security implications.

Diff

diff --git a/documentdb/latest/developerguide/substr.md b/documentdb/latest/developerguide/substr.md
index 8b1378917..d984b07b8 100644
--- a//documentdb/latest/developerguide/substr.md
+++ b//documentdb/latest/developerguide/substr.md
@@ -0,0 +1 @@
+[](/pdfs/documentdb/latest/developerguide/developerguide.pdf#substr "Open PDF")
@@ -1,0 +3,126 @@
+[Documentation](/index.html)[Amazon DocumentDB](/documentdb/index.html)[Developer Guide](what-is.html)
+
+Example (MongoDB Shell)Code examples
+
+# $substr
+
+The `$substr` operator in Amazon DocumentDB is used to extract a substring from a given string. It is particularly useful when you need to define substrings based on a range of characters, rather than a range of bytes. This is especially important when dealing with Unicode strings, where the number of bytes used to represent a character can vary.
+
+**Parameters**
+
+  * `string`: The input string from which to extract the substring.
+
+  * `start`: The starting position (zero-based) of the substring to be extracted. Can be a non-negative integer expression.
+
+  * `length`: The number of characters in the extracted substring. Can be a non-negative integer expression.
+
+
+
+
+## Example (MongoDB Shell)
+
+In this example, we'll demonstrate the use of `$substr` to extract the state abbreviation from an employee's desk location.
+
+**Create sample documents**
+    
+    
+    db.people.insertMany([
+      { "_id": 1, "Desk": "Düsseldorf-NRW-021" },
+      { "_id": 2, "Desk": "Bremerhaven-HBB-32a" },
+      { "_id": 3, "Desk": "Norderstedt-SHH-892.50" },
+      { "_id": 4, "Desk": "Brandenburg-BBB-78" }
+    ]);
+
+**Query example**
+    
+    
+    db.people.aggregate([
+      {
+        $project: {
+          "state": { $substr: ["$Desk", 12, 3] }
+        }
+      }
+    ])
+
+**Output**
+    
+    
+    { "_id": 1, "state": "NRW" },
+    { "_id": 2, "state": "HBB" },
+    { "_id": 3, "state": "SHH" },
+    { "_id": 4, "state": "BBB" }
+
+## Code examples
+
+To view a code example for using the `$substr` 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("people");
+    
+      const result = await collection.aggregate([
+        {
+          $project: {
+            "state": { $substrCP: ["$Desk", 12, 3] }
+          }
+        }
+      ]).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["people"]
+    
+        result = list(collection.aggregate([
+            {
+                "$project": {
+                    "state": { "$substrCP": ["$Desk", 12, 3] }
+                }
+            }
+        ]))
+    
+        print(result)
+        client.close()
+    
+    example()
+
+![Warning](https://d1ge0kk1l5kms0.cloudfront.net/images/G/01/webservices/console/warning.png) **Javascript is disabled or is unavailable in your browser.**
+
+To use the Amazon Web Services Documentation, Javascript must be enabled. Please refer to your browser's Help pages for instructions.
+
+[Document Conventions](/general/latest/gr/docconventions.html)
+
+$strcasecmp
+
+$substrBytes
+
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+
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+
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