Group result by 15 minutes time interval in MongoDb

Question

I have a \"status\" collection like this strcture -

{
    _id: ObjectId(\"545a0b63b03dbcd1238b4567\"),
    status: 1004,
    comment: \"Rem dolor ipsam place         


        

Answer 1

I like the other answer here, and mostly for the use of date math instead of aggregation date operators which while helpful can also be a little obscure.

The only thing I want to add here is that you can also return a Date object from the aggregation framework by this approach as opposed to the "numeric" timestamp as the result. It's just a little extra math on the same principles, using $add:

db.collection.aggregate([
    { "$group": {
        "_id": {
            "$add": [
                { "$subtract": [
                    { "$subtract": [ "$current_date", new Date(0) ] },
                    { "$mod": [ 
                        { "$subtract": [ "$current_date", new Date(0) ] },
                        1000 * 60 * 15
                    ]}
                ] },
                new Date(0)
            ]
        },
        "count": { "$sum": 1 }
    }}
])

The Date(0) contructs in JavaScript here represent the same "epoch" date in a shorter form, as 0 millisecond from epoch is epoch. But the main point is that when the "addition" to another BSON date object is done with a numeric identifier, then the inverse of the described condition is true and the end result is actually now a Date.

All drivers will return the native Date type to their language by this approach.