Group result by 15 minutes time interval in MongoDb -

i have "status" collection strcture -

{     _id: objectid("545a0b63b03dbcd1238b4567"),     status: 1004,     comment: "rem dolor ipsam placeat omnis non. aspernatur nobis qui nisi similique.",     created_at: isodate("2014-11-05t11:34:59.804z") }, {     _id: objectid("545a0b66b03dbcd1238b4568"),     status: 1001,     comment: "sint et eos vero ipsa voluptatem harum. hic unde voluptatibus et blanditiis quod modi.",     created_at: isodate("2014-11-05t11:35:02.814z") } .... .... 

i need result grouped 15 minutes interval collection.

there couple of ways this.

the first date aggregation operators, allow dissect "date" values in documents. "grouping" primary intent:

db.collection.aggregate([     { "$group": {         "_id": {             "year": { "$year": "$created_at" },             "dayofyear": { "$dayofyear": "$created_at" },             "interval": {                 "$subtract": [                      { "$minute": "$created_at" },                     { "$mod": [{ "$minute": "$created_at"}, 15] }                 ]             }         }},         "count": { "$sum": 1 }     }} ]) 

the second way using little trick of when date object subtracted (or other direct math operation) date object, result numeric value representing epoch timestamp milliseconds between 2 objects. using epoch date epoch milliseconds representation. use date math interval:

db.collection.aggregate([     { "$group": {         "_id": {             "$subtract": [                 { "$subtract": [ "$current_date", new date("1970-01-01") ] },                 { "$mod": [                      { "$subtract": [ "$current_date", new date("1970-01-01") ] },                     1000 * 60 * 15                 ]}             ]         },         "count": { "$sum": 1 }     }} ]) 

so depends on kind of output format want grouping interval. both represent same thing , have sufficient data re-construct "date" object in code.

you can put else want in "grouping operator" portion after grouping _id. i'm using basic "count" example in lieu of real statement want do.