I have following documents:

{
usera:{
    data: {
        order1: "data",
        order2: "data2",
        order3: "data3",
    }
},
userb:{
    data: {
        order1: "data",
        order2: "data2",
    }
},
userc:{
    data: {
        order1: "data",
        order3: "data3",
    }
},
userd:{
    data: {
        order1: "data",
        order2: "data2",
        order3: "data3",
    }
},
usere:{
    data: {
        order1: "data"
    }
}
}

I want to query documents which has only order1 and no other order2 or other documents are available.

For example only usere is a document that has order1 and others do not exists.

Is there anyway, where I can check length of my data field and if it is 1 and order1 $exists is true

CodePudding user response：

I think the below code is what you are looking for

db.collection.aggregate([
  {
    "$match": {
      "$expr": {
        "$eq": [
          {
            "$let": {
              "vars": {
                "orderElem": {
                  "$objectToArray": "$user.data"
                },
                
              },
              "in": "$$orderElem.k"
            },
            
          },
          [
            "order1"
          ],
          
        ],
        
      }
    },
    
  }
])

MongoPlayground Example