Question 270987 in Mongodb Question posted in
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How to bring values from array of embedded documents into the root on MongoDB?

I have the following record:

id: 119,
customfields: Array (2)

  0: Object
    value: "Mr"
    type: "salutation"

  1: Object
    value: "Google"
    type: "company"

I need to update this document so that I get:


id: 119,
salutation: "Mr",
company: "Google"

Important is:

  • The position of the arguments can vary, ie, some records have salutation first, others have company and other may have other fields that do not matter.
  • some documents do not have the salutation records inside the customfields array and therefore should just be ignored. Same logic for the company.
Tags:

2

Answers


  1. 0

    $map customfields to an array of k-v tuple first. Then, $mergeObjects with $$ROOT object to get the final object. $unset the now useless customfields and $merge by id to update back to the document.

    db.collection.aggregate([
  {
    "$match": {
      "id": 119
    }
  },
  {
    "$set": {
      "customfields": {
        "$arrayToObject": {
          "$map": {
            "input": "$customfields",
            "as": "cf",
            "in": {
              "k": "$$cf.type",
              "v": "$$cf.value"
            }
          }
        }
      }
    }
  },
  {
    "$replaceRoot": {
      "newRoot": {
        "$mergeObjects": [
          "$$ROOT",
          "$customfields"
        ]
      }
    }
  },
  {
    "$unset": "customfields"
  },
  {
    "$merge": {
      "into": "collection",
      "on": "id"
    }
  }
])

    Mongo Playground

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  2. 0

    Here’s another way to do it using "$reduce" to rebuild the document.

    db.collection.update({
  "id": 119
},
[
  {
    "$set": {
      "newRoot": {
        "$reduce": {
          "input": "$customfields",
          "initialValue": {
            "id": "$id"
          },
          "in": {
            "$mergeObjects": [
              "$$value",
              {
                "$arrayToObject": [
                  [
                    {
                      "k": "$$this.type",
                      "v": "$$this.value"
                    }
                  ]
                ]
              }
            ]
          }
        }
      }
    }
  },
  {"$replaceWith": "$newRoot"}
])

    Try it on mongoplayground.net.

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