How to transform an array of objects into fields in the parent object in MongoDB?

Question

I have a collection where every document has this kind of structure:

{
  docName: "Document Name",
  probabilities: [
            { topicName:"topic1", prob: 0.3  },
            { topicName:"topic2", prob: 0.4  }, 
            { topicName:"topic3", prob: 0.23 }
              ...
            ]
 otherField: data,
 ...
}

I need to trnaform them into something like this:

{
  docName: "Document Name",
  topic1: 0.3,
  topic2: 0.4, 
  topic3: 0.23,
  ...
  otherField: data,
  ...
}

I tried using $arrayToObject and $objectToArray but I didn't figure out how to make it work.

Thanks in advance for your help!

Ashh · Accepted Answer · 2019-07-02 17:53:03Z

2

You can use below aggregation

db.collection.aggregate([
  { "$replaceRoot": {
    "newRoot": {
      "$mergeObjects": [
        "$$ROOT",
        { "$arrayToObject": {
          "$map": {
            "input": "$probabilities",
            "in": {
              "k": "$$this.topicName",
              "v": "$$this.prob"
            }
          }
        }}
      ]
    }
  }},
  { "$project": { "probabilities": 0 }}
])

MongoPlayground

answered Jul 2, 2019 at 17:53

Ashh

46.6k16 gold badges111 silver badges137 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

How to transform an array of objects into fields in the parent object in MongoDB?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related