How to query for getting projected values from lookup pipeline as key pair in mongoose

{
$lookup:{
  from:'response',
  localField:'_id',
  foreignField:'user',
  as:'dataResponse'
  pipeline:[{project:{ resId:1,status:1}]
}



email : "[email protected]"
dataRespose : [ 
{_id: '63515eea05c8c884a33b291d', resId: '632f2d8e470895396dccefdb', status: 'IN_PROGRESS'} ,
{_id: '6385ee9f451fa8879071bcde', resId: '63771adafa3b611596aaa15d', status: 'CREATED'}`]

how to get like this

email : "[email protected]"
dataRespose : {
632f2d8e470895396dccefdb : 'IN_PROGRESS' ,
63771adafa3b611596aaa15d : 'CREATED'
}

CodePudding user response：

One way that you can create an object using values for the field names is by using the $arrayToObject operator. In the example below, we use that operator inside of a subsequent $addFields stage and $map over the dataResponse array that is returned by the preceding $lookup. During that processing we generate the object document with the k and v fields (needed for $arrayToObject set to the values from the fields that you are interested in (resId and status):

  {
    "$addFields": {
      "dataResponse": {
        "$arrayToObject": {
          "$map": {
            "input": "$dataResponse",
            "in": {
              k: "$$this.resId",
              v: "$$this.status"
            }
          }
        }
      }
    }
  }

Output:

[
  {
    "_id": 1,
    "dataResponse": {
      "632f2d8e470895396dccefdb": "IN_PROGRESS",
      "63771adafa3b611596aaa15d": "CREATED"
    },
    "email": "[email protected]"
  }
]

Playground example here.

You could do something similar inside of the pipeline embedded in the $lookup if you desired, but functionally the results will be the same.