Spring Data Mongodb sort inner array

Question

I have been trying to sort the items stored in a list within a document based on date. Here is the structure of my document:

{
  "_id": ObjectId("55c1940ce4b0a2a0482f22e8"),
  "eventId": "45b73f69-4804-4b50-84d0-6c551aa5bb5c",
  "isMacro": true,
  "isDeleted": false,
  "calendarEvent": [
    {
      "eventId": "b89a1519-ddff-4f71-9366-117e23c16d5c",
      "startDateTime": ISODate("2017-04-16T10:00:00.000Z")
    },
    {
      "eventId": "ecec8b3a-cf48-4f14-a7ac-14cd1a19f9da",
      "startDateTime": ISODate("2014-03-25T10:00:00.000Z")
    },
    {
      "eventId": "a002cc47-2939-4e75-9793-74720ebb7a21",
      "startDateTime": ISODate("2015-09-10T10:00:00.000Z")
    }
  ]
}

I want to sort the items in calendarEvent list in ASC order. I'm using the Spring Data MongoDB. Here is my code:

AggregationOperation unwind = Aggregation.unwind("calendarEvent");
AggregationOperation match = Aggregation.match(criteria);
AggregationOperation project = getEventProjectionFields(); //private function which returns project object.
AggregationOperation sort = Aggregation.sort(Direction.ASC,
        "calendarEvent.startDateTime");

Aggregation aggregation = Aggregation.newAggregation(unwind, match,
        project, skip(0), limit(5), sort);

AggregationResults<Event> groupResults = mongoTemplate.aggregate(
        aggregation, mongoTemplate.getCollectionName(KAEvent.class),
        Event.class);

return groupResults.getMappedResults();

Printing the value of aggregation.toString() returns the following JSON:

{
  "aggregate": "__collection__",
  "pipeline": [
    {
      "$unwind": "$calendarEvent"
    },
    {
      "$match": {
        "isMacro": true,
        "isDeleted": false,
        "$and": [
          {
            "eventId": {
              "$in": [
                "3d478f1a-9296-46b5-87d9-d0b442be0309",
                "4cbbe84b-6a35-4797-8c06-9b9b679ca48c"
              ]
            }
          },
          {
            "calendarEvent.eventId": {
              "$in": [
                "cb3fb7e7-5444-4ca5-8a6b-09e74bd346e4",
                "fec94eb6-160d-4608-8dae-5b43b88c550f",
                "e33d11a1-6d36-49ce-9e84-9b83ee9445dd"
              ]
            }
          }
        ],
        "calendarEvent.startDateTime": {
          "$gte": {
            "$date": "2015-10-13T07:42:48.841Z"
          }
        }
      }
    },
    {
      "$project": {
        "eventId": "$calendarEvent.eventId",
        "name": "$calendarEvent.name",
        "eventDescription": "$calendarEvent.eventDescription",
        "eventSummary": "$calendarEvent.eventSummary",
        "eventLocation": "$calendarEvent.eventLocation",
        "startDateTime": "$calendarEvent.startDateTime",
        "endDateTime": "$calendarEvent.endDateTime",
        "lastUpdateDate": "$calendarEvent.lastUpdateDate",
        "eventUrl": "$calendarEvent.eventUrl",
        "customImageUrl": "$calendarEvent.customImageUrl",
        "tagsList": "$calendarEvent.tagsList",
        "imagesList": "$calendarEvent.imagesList",
        "isFeatured": "$calendarEvent.isFeatured",
        "isDeleted": "$calendarEvent.isDeleted",
        "providerId": 1,
        "sourceId": 1,
        "isMacro": 1,
        "isCalendarEvent": 1,
        "_class": "$calendarEvent._class",
        "parenteventId": "$eventId"
      }
    },
    {
      "$skip": 0
    },
    {
      "$limit": 5
    },
    {
      "$sort": {
        "calendarEvent.startDateTime": 1
      }
    }
  ]
}

After all this, the results return are not sorted. Am I missing something here or doing something wrong?

chridam · Accepted Answer · 2015-10-13 11:40:59Z

2

You are doing a sort after you project the new field startDateTime which is derived from the embedded field "calendarEvent.startDateTime".

Change the sort pipeline to

AggregationOperation sort = Aggregation.sort(Direction.ASC,
        "startDateTime");

answered Oct 13, 2015 at 11:40

chridam

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3 Comments

Sibtain Norain Over a year ago

Tried this as well but still getting incorrect sorting order.

chridam Over a year ago

Have you also tried placing the sort just before the limit pipeline as suggested in the docs here and there for better performance?

shkhssn Over a year ago

@SibtainNorain : I'm having the same requirement and still not able to make it work. Could you please confirm this solution suggested by Chridam work for you and no other changes you made to your original code above?

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