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Count Documents
Note
If you specify a callback method, countDocuments() and
estimatedDocumentCount() return nothing. If you do not specify one,
this method returns a Promise that resolves to the result object
when it completes. See our guide on Promises and Callbacks for more information, or the
API documentation for
information on the result object.
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_" });
Example
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.
Note
You can use this example to connect to an instance of MongoDB and interact with a database that contains sample data. To learn more about connecting to your MongoDB instance and loading a sample dataset, see the Usage Examples guide.
Note
Identical Code Snippets
The JavaScript and TypeScript code snippets above are identical. There are no TypeScript specific features of the driver relevant to this use case.
If you run the preceding sample code, you should see the following output:
Estimated number of documents in the movies collection: 23541 Number of movies from Canada: 1349