I'm trying to group documents by date with the Mongo aggregation framework. I've tried a bunch of things and can't identify the problem. My query looks like this:

// get current date and then get the date 8 months ago
var now = Date.now()
var lastMonth = 60*60*24*30*1000*8
lastMonth = now - lastMonth

var query = {
                type: 'something',
                deleted: {$ne: true},
                created: {$gte: lastMonth}
            }

    var stickerNames = [];
    db.Message.aggregate([{$match: query},
        {$group:
            {_id: {data: '$data',
                    month: {$month: '$created'},
                    year: {$year: '$created'}
                    },
            count:{$sum: 1}
            }
        },
        {$sort:
            {count: 1}}],
        function(err, stuff){
            if(err){
                return res.json({error: err.message})
            }
            else{
                return res.json({data: stuff})
            }
    })

I've tried a ton of different things with the dates and checked other SO posts, but nothing has worked so far. If I take out the created: {$gte: lastMonth} clause then it returns every document of type 'something'. If I leave it, it returns no documents.

The created field is set in the model by

created: {type: Date, default: Date.now}

I'm trying to group documents by date with the Mongo aggregation framework. I've tried a bunch of things and can't identify the problem. My query looks like this:

// get current date and then get the date 8 months ago
var now = Date.now()
var lastMonth = 60*60*24*30*1000*8
lastMonth = now - lastMonth

var query = {
                type: 'something',
                deleted: {$ne: true},
                created: {$gte: lastMonth}
            }

    var stickerNames = [];
    db.Message.aggregate([{$match: query},
        {$group:
            {_id: {data: '$data',
                    month: {$month: '$created'},
                    year: {$year: '$created'}
                    },
            count:{$sum: 1}
            }
        },
        {$sort:
            {count: 1}}],
        function(err, stuff){
            if(err){
                return res.json({error: err.message})
            }
            else{
                return res.json({data: stuff})
            }
    })

I've tried a ton of different things with the dates and checked other SO posts, but nothing has worked so far. If I take out the created: {$gte: lastMonth} clause then it returns every document of type 'something'. If I leave it, it returns no documents.

The created field is set in the model by

created: {type: Date, default: Date.now}

• javascript
• mongodb
• aggregation-framework

• 2 A Date object minus number returns the timestamp value and not the number of milliseconds. You should be doing: lastMonth = new Date(now - lastMonth) ` – Blakes Seven Commented Jul 5, 2015 at 23:45

1 Answer 1

As far as I understand, "group by date" means group by "day-month-year". Maybe are you missing the $dayOfMonth aggregation function?

Given this sample data set:

> db.w.find({})
{ "_id" : ObjectId("55503d31a3d32cf6295ad897"),
  "created" : ISODate("2014-12-08T12:00:00Z"),
  "data" : 1 }
{ "_id" : ObjectId("55503d43a3d32cf6295ad898"),
  "created" : ISODate("2014-12-08T08:00:00Z"),
  "data" : 2 }
{ "_id" : ObjectId("55503d4ba3d32cf6295ad899"),
  "created" : ISODate("2014-12-08T20:00:00Z"),
  "data" : 3 }
{ "_id" : ObjectId("55503d55a3d32cf6295ad89a"),
  "created" : ISODate("2014-12-06T20:00:00Z"),
  "data" : 4 }
{ "_id" : ObjectId("55503d77a3d32cf6295ad89c"),
  "created" : ISODate("2015-12-08T20:00:00Z"),
  "data" : 5 }

And that aggregate pipeline:

> db.w.aggregate([
       {$group:
         {
           _id: 
             {
               day: {$dayOfMonth: "$created"},
               month: {$month: "$created"}, 
               year: {$year: "$created"}
             }, 
             total: {$sum: "$data"},
             count: {$sum: 1}
          }
        },
        {$sort: {count: 1}}
])

You will get back the expected oute:

{ "_id" : { "day" : 8, "month" : 12, "year" : 2015 }, "total" : 5, "count" : 1 }
{ "_id" : { "day" : 6, "month" : 12, "year" : 2014 }, "total" : 4, "count" : 1 }
{ "_id" : { "day" : 8, "month" : 12, "year" : 2014 }, "total" : 6, "count" : 3 }