Count Documents
Overview
In this guide, you can learn how to count the number of documents in your MongoDB collections. The Node.js driver provides two methods for counting documents in a collection:
collection.countDocuments() returns the number of documents in the collection that match the specified query. If you specify an empty query document,
countDocuments()returns the total number of documents in the collection.collection.estimatedDocumentCount() returns an estimation of the number of documents in the collection based on collection metadata.
estimatedDocumentCount() is faster than countDocuments() because
the estimation uses the collection's metadata rather than scanning the
collection. In contrast, countDocuments() takes longer to return, but
provides an accurate count of the number of documents and supports
specifying a filter. Choose the appropriate method for your workload.
To specify which documents you wish to count, countDocuments()
accepts a query parameter.
countDocuments() counts the documents that match the specified query.
countDocuments() and estimatedDocumentCount() support optional
settings that affect the method's execution. Refer to the reference
documentation for each method for more information.
Tip
You can improve performance when using countDocuments() to return the
total number of documents in a collection by avoiding a collection scan. To
do this, use a hint to take
advantage of the built-in index on the _id field. Use this technique only
when calling countDocuments() with an empty query parameter.
collection.countDocuments({}, { hint: "_id_" });
countDocuments() Example: Full File
Note
Example Setup
This example connects to an instance of MongoDB by using a
connection URI. To learn more about connecting to your MongoDB
instance, see the Connect to MongoDB guide. This example
also uses the movies collection in the sample_mflix database
included in the Atlas sample datasets. You
can load them into your database on the free tier of MongoDB Atlas by
following the Get Started with Atlas Guide.
Note
No TypeScript Specific Features
The following code example uses JavaScript. There are no TypeScript specific features of the driver relevant to this use case.
The following example estimates the number of documents in the
movies collection in the sample_mflix database, and then returns
an accurate count of the number of documents in the movies
collection with Canada in the countries field:
1 // Count documents in a collection 2 3 import { MongoClient } from "mongodb"; 4 5 // Replace the uri string with your MongoDB deployment's connection string 6 const uri = "<connection string uri>"; 7 8 const client = new MongoClient(uri); 9 10 async function run() { 11 try { 12 const database = client.db("sample_mflix"); 13 const movies = database.collection("movies"); 14 15 /* Print the estimate of the number of documents in the 16 "movies" collection */ 17 const estimate = await movies.estimatedDocumentCount(); 18 console.log(`Estimated number of documents in the movies collection: ${estimate}`); 19 20 /* Print the number of documents in the "movies" collection that 21 match the specified query */ 22 const query = { countries: "Canada" }; 23 const countCanada = await movies.countDocuments(query); 24 console.log(`Number of movies from Canada: ${countCanada}`); 25 } finally { 26 // Close the connection after the operations complete 27 await client.close(); 28 } 29 } 30 // Run the program and print any thrown exceptions 31 run().catch(console.dir);
Running the preceding sample code results in the following output:
Estimated number of documents in the movies collection: 23541 Number of movies from Canada: 1349
API Documentation
To learn more about any of the types or methods discussed in this guide, see the following API documentation: