I have a collection like this:

[
  {
    "key": 1,
    "form_details": {
      "PROJECT": "RD",
      "INTERESTING": true
    }
  },
  {
    "key": 2,
    "form_details": {
      "PROJECT": "RC",
      "INTERESTING": true
    }
  }
]

I would update the embedded field “form_details.INTERESTING” to false if “form_details.PROJECT” is “RD”, and maintain current value elseware.

I found this solution:

db.collection.update({},
{
  $set: {
    "form_details.INTERESTING": {
      $cond: {
        if: {
          $eq: [
            "$form_details.PROJECT",
            "RD"
          ]
        },
        then: false,
        else: "$form_details.INTERESTING"
      }
    }
  }
})

But it works wrong, updating all the value under $cond as an Object if condition is met:

[
  {
    "_id": ObjectId("5a934e000102030405000000"),
    "form_details": {
      "INTERESTING": {
        "$cond": {
          "else": "$form_details.INTERESTING",
          "if": {
            "$eq": [
              "$form_details.PROJECT",
              "RD"
            ]
          },
          "then": false
        }
      },
      "PROJECT": "RD"
    },
    "key": 1
  },
  {
    "_id": ObjectId("5a934e000102030405000001"),
    "form_details": {
      "INTERESTING": true,
      "PROJECT": "RC"
    },
    "key": 2
  }
]

I would simply update it to “false” value if that condition is met.

Here is the example playground:

https://mongoplayground.net/p/d1uSCHxvwAm