Does running count() incur a read for the documents counted?

[Prasad_Saya]

Hello @Travis_Aucoin, welcome to the MongoDB Community forum!

MongoDB NodeJS Driver API has three Collection class methods related with counting documents:

countDocuments: Gets the number of documents matching the filter. This gets the accurate count.

For a fast count of the total documents in a collection see estimatedDocumentCount: Gets an estimate of the count of documents in a collection using collection metadata.

count: An estimated count of matching documents in the db to a filter. NOTE: This method has been deprecated, since it does not provide an accurate count of the documents in a collection. To obtain an accurate count of documents in the collection, use countDocuments. To obtain an estimated count of all documents in the collection, use estimatedDocumentCount.

There is also a FindCursor#count: Get the count of documents for this cursor. This method is deprecated. Use collection.estimatedDocumentCount or collection.countDocuments instead.

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Related References:

About golang mongo driver CountDocuments

why not use count?why using aggregation group?

How to optimize a count query

Using the c# driver to get a document count, using CountDocumentsAsync is see the following “very slow” command in Atlas profiler: { "command": { "aggregate": "contacts", "pipeline": [ { "$match": { "accountId": 158, "deleted": null } }, { "$group": { "_id": 1, "n": { "$sum": 1 } } } ], "cursor": {}, "$db": "Loopify", "lsid": { "id": { "$u…