$strLenBytes

The $strLenBytes operator in Amazon DocumentDB is used to determine the length of a string in bytes. This is useful when you need to understand the storage size of a string field, especially when dealing with Unicode characters that may use more than one byte per character.

Parameters

• expression: The string expression to calculate the length of.

Example (MongoDB Shell)

This example demonstrates how to use the $strLenBytes operator to calculate the length of string fields in bytes.

Create sample documents

db.people.insertMany([
  { "_id": 1, "Desk": "Düsseldorf-BVV-021" },
  { "_id": 2, "Desk": "Munich-HGG-32a" },
  { "_id": 3, "Desk": "Cologne-ayu-892.50" },
  { "_id": 4, "Desk": "Dortmund-Hop-78" }
]);

Query example

db.people.aggregate([
  {
    $project: {
      "Desk": 1,
      "length": { $strLenBytes: "$Desk" }
    }
  }
])

Output

{ "_id" : 1, "Desk" : "Düsseldorf-BVV-021", "length" : 19 }
{ "_id" : 2, "Desk" : "Munich-HGG-32a", "length" : 14 }
{ "_id" : 3, "Desk" : "Cologne-ayu-892.50", "length" : 18 }
{ "_id" : 4, "Desk" : "Dortmund-Hop-78", "length" : 15 }

Note that the length of the "Düsseldorf-BVV-021" string is 19 bytes, which is different from the number of code points (18) due to the Unicode character "Ü" occupying 2 bytes.

Code examples

To view a code example for using the $strLenBytes 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: {
        "Desk": 1,
        "length": { $strLenBytes: "$Desk" }
      }
    }
  ]).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.test
    collection = db.people

    result = list(collection.aggregate([
        {
            '$project': {
                "Desk": 1,
                "length": { "$strLenBytes": "$Desk" }
            }
        }
    ]))

    print(result)
    client.close()

example()