mongodb - aggregation cursor count

Question

I was reading the API documentation (and was experimenting a bit), but it seems that cursor.count() no longer exists, so I was wondering if it was possible to get a count of your aggregate. This is because I would like to know how many documents there are in total, while still limiting and skipping results. I'm currently using $facet to facilitate this, but unsure if there's a better method.

{
    $facet: 
    {
        "results": 
        [
            {
                "$skip": 
                    start
            },
            {
                "$limit": 
                    finish
            },
        ],
        "total": 
        [
            {
                "$count": 
                    "total" 
            },
        ]
    }
}

Answer 1

Using $facet for this use case is fine, both for style and performance. It should be noted, though, that this is essentially two queries in one, albeit server-side optimized. Getting the full count of the filtered material (or no filter at all if no initial $match ) takes time regardless of the $skip/$limit setup. If the $match produces a relatively small amount of material, then $count will be fast. The dynamics involved are very similar to those in the regular SQL world, eg Run a query with a LIMIT/OFFSET and also get the total number of rows