How to aggregate on nested embedded object in MongoDB

Question

{
  "_id": 1,
  "title": {
    header1:{ "name":"A" , age:10, "active":true},
    header2:{ "name":"B" , age:15, "active":false},
    header3:{ "name":"C" , age:20, "active":true},
    header4:{ "name":"D" , age:30, "active":true},
    header5:{ "name":"E" , age:35, "active":false},
    header6:{ "name":"F" , age:40, "active":true},
    header7:{ "name":"G" , age:45, "active":false},
  }
}

How can I show only those headers whose active value is false?

Yong Shun · Accepted Answer · 2021-12-21 14:59:31Z

1

$project

1.1 Convert key-value pair to array via $objectToArray for headers field . 1.2 $filter with $$this.v.active which is false.
$project

2.1 Convert headers to key-value pair via $arrayToObject and assign to title field.

db.collection.aggregate([
  {
    $project: {
      _id: 1,
      headers: {
        $filter: {
          "input": {
            $objectToArray: "$title"
          },
          "cond": {
            "$eq": [
              "$$this.v.active",
              false
            ]
          }
        }
      }
    }
  },
  {
    $project: {
      _id: 1,
      title: {
        "$arrayToObject": "$headers"
      }
    }
  }
])

Sample Mongo Playground

answered Dec 21, 2021 at 14:59

Yong Shun

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