CODEWITHSUNDEEP
mongodbpipelineaggregation
Viriato
Viriato

Reputation: 683

How to sort an array of `$lookup` result by `Date` field

I'm trying to sort an array (descending) that gets computed through a $lookup by a field called createdAt which contains a Date object:

[
   {
      "$lookup": {
         "from": "activities",
         "localField": "activities",
         "foreignField": "_id",
         "as": "activities"
      }
   },
   {
      "$sort": {
         "activities.createdAt": -1
      }
   },
   {
      "$project": {
         "_id": false,
         "updatedAt": false,
         "activities._id": false,
         "activities.game": false,
         "activities.updatedAt": false,
         "activities.__v": false,
         "__v": false
      }
   }
]

The activities field is being "populated" correctly but it's not sorting the results.

Upvotes: 0

Views: 529

Answers (1)

Takis
Takis

Reputation: 8695

Try to replace your lookup with a lookup with pipeline like the bellow. If you want the array to be sorted, you can do it inside that pipeline.

If this isn't what you need if you can add some sample data and expected output.

aggregate(
[{"$lookup": 
   {"from": "activities",
    "localField": "activities",
    "foreignField": "_id",
    "pipeline": [{"$sort": {"createdAt": -1}}],
    "as": "activities"}}])

Upvotes: 1

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