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kotlinlang

Uh, interesting.

The MongoDB Java driver's `MongoCollection.countDocuments()` does not call <https://www.mongodb.com/docs/manual/reference/method/db.collection.countDocuments/|db.countDocuments()>, but executes
```aggregate([
    {
        "$match": {}
    },
    {
        "$group": {
            "_id": 1,
            "n": {
                "$sum": 1
            }
        }
    }
])```


Why could this be the case? is there a scenario that this is more efficient?

I'm thinking maybe the Java implementation is older than the db method? But that sounds strange, I think it's older than aggregation pipelines.

I doubt that the Java implementation came before aggregations

The empty `$match` is weird to me. It shouldn't be that hard to remove it? It's 69 pointless bytes.