mongodb aggregation: get all values for the particular field in list-CodePudding

I have collections like:

[
  {
    "_id": "1",
    "religion": "south",
    "tested": true,
    "fruit": "orange",
    "created_at": 2211123333
  },
  {
    "_id": "2",
    "religion": "north",
    "tested": false,
    "fruit": "apple",
    "created_at": 223444433
  },
  {
    "_id": "3",
    "religion": "north",
    "tested": true,
    "fruit": "orange",
    "created_at": 234567876
  }
]

if religion is south and tested is true then get all the values of fruits in list.

tried:

pipeline = [{"$match": {"$and": [{"religion": "south"}, {"tested": true}]}}, {}{"$project": {"fruit": 1, "_id": 0}}]
db.collection.aggregate(pipeline).to_list(length=None)

getting result as : [{"fruit": "orange"}, {"fruit": "apple"}]

but result should be like: {"fruit" : ["orange", "apple"]}

CodePudding user response：

use $group, $addToSet and using$cond you don't need the $match stage

test it at mongoPlayground

[
  {
    "$group": {
      "_id": null,
      "fruit": {
        "$addToSet": {
          "$cond": [
            {
              "$and": [
                {
                  "$eq": [
                    "$religion",
                    "south"
                  ]
                },
                {
                  "$eq": [
                    "$tested",
                    true
                  ]
                }
              ]
            },
            "$fruit",
            "$$REMOVE"
          ]
        }
      }
    }
  },
  {
    "$project": {
      fruit: 1,
      _id: 0
    }
  }
]