CODEWITHSUNDEEP
mongodb
lushuming
lushuming

Reputation: 29

How can I count the number of documents grouping by nested Array?

I have some documents like :

{
    "product" : [{
        "name" : "apple",
        "seller" : [
            {
                "name" : "Alice",
                "gender" : 1
            },
            {
                "name" : "Bob",
                "gender" : 0
            }
        ]
    }, {
        "name" : "anotherApple",
        "seller" : [
            {
                "name" : "Bob",
                "gender" : 0
            }
        ]
    }],
    "date" : "someDay"
},
{
    "product" : [{
        "name" : "apple",
        "seller" : [
            {
                "name" : "Alice",
                "gender" : 1
            },
            {
                "name" : "CName",
                "gender" : 0
            }
        ]
    }],
    "date" : "someDay"
}

And I wanna count the number of one seller's bills, in this case , which is supposed to be :

{
    "Alice" : 2,
    "Bob" : 1,
    "CName" : 1
}

I have tried some ways such like unwind seller in product but none of them works. How can I do this?

Upvotes: 0

Views: 32

Answers (1)

AlexisG
AlexisG

Reputation: 2484

I used addToSet to have a list of ids. And count them with $sizein a project

db.collection.aggregate({
  "$unwind": "$product"
},
{
  "$unwind": "$product.seller"
},
{
  $group: {
    _id: "$product.seller.name",
    list_ids: {
      "$addToSet": "$_id"
    }
  }
},
{
  $project: {
    "_id": 1,
    "size": {
      $size: "$list_ids"
    }
  }
})

Witch gives me

[
  {
    "_id": "CName",
    "size": 1
  },
  {
    "_id": "Alice",
    "size": 2
  },
  {
    "_id": "Bob",
    "size": 1
  }
]

Try it here

Upvotes: 2

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