How to do I Aggregate group by Year/Month/Day using the C# driver.

[Colin G]

I am trying to get a count of documents in my collection by year/month/day. 

I have been able to piece together the following query but it does not want to return any results. 

   var aggregate = this.collection.Aggregate()

                .Match(filterDefinition)

               .Group(new BsonDocument { { "_id",

                   new BsonDocument {

                       { "month", new BsonDocument("$month", "$timestamp") },

                   { "day", new BsonDocument("$dayOfMonth", "$timestamp") },

                   { "year", new BsonDocument("$year", "$timestamp") } } },

                   { "count", new BsonDocument("$sum", 1) } });

         

            IAsyncCursor<BsonDocument> asyncCursor = aggregate.ToCursor();

            var x = asyncCursor.ToList();

when I run this query in RoboMongo it throws an exception

db.getCollection('MyCollection).aggregate([

{ "$match" : { "filter_key" : "uniquefilterKey-123456", "@timestamp" : 

    { "$gte" : ISODate("2017-01-18T05:57:00Z"), 

        "$lte" : ISODate("2017-05-18T06:12:00Z") } } }, 

    { "$group" : { "_id" : { 

    "eventSource" :  "$eventSource" }, 

    "day" : { "$dayOfMonth" : "$timestamp" }, 

    "year" : { "$year" : "$timestamp" } 

    },

    "count" : { "$sum" : 1 } } }]).find({})

assert: command failed: {

"ok" : 0,

"errmsg" : "unknown group operator '$dayOfMonth'",

"code" : 15952,

"codeName" : "Location15952"

} : aggregate failed

_getErrorWithCode@src/mongo/shell/utils.js:23:13

doassert@src/mongo/shell/assert.js:13:14

assert.commandWorked@src/mongo/shell/assert.js:266:5

DBCollection.prototype.aggregate@src/mongo/shell/collection.js:1215:5

@(shell):1:1

Any help would be appreciated. 

Thanks

[Shiv]

$dayOfMonth / any other date time operator are not group accumulator. 

So your $group stage should look like

 {

  "$group": {

  "_id": {

  "eventSource": "$eventSource",

  "day": {

  "$dayOfMonth": "$timestamp"

  },

  "year": {

  "$year": "$timestamp"

  }

  },

  "count": {

  "$sum": 1

  }

  }

 },