CODEWITHSUNDEEP
mongodbmongodb-queryaggregation-framework
Kamlesh Kanazariya
Kamlesh Kanazariya

Reputation: 1259

Add a new field in every document through aggregation & $facet in mongodb

My Sample data looks like below:

Category      response
Privacy         1
Mobile          1
Privacy         1
Privacy         2

I want add new field Total taken from sum of all response field values. Required output as below :

Category      response   Total
Privacy         1         5
Mobile          1         5
Privacy         1         5
Privacy         2         5

How can I get this output in mongodb.

Upvotes: 3

Views: 1203

Answers (1)

whoami - fakeFaceTrueSoul
whoami - fakeFaceTrueSoul

Reputation: 17915

Update : As value of Total is not the fixed one, updated answer with question :

/** Using 'facet' as we need docs to be returned in result 
  * (Can also be done without 'facet' by pushing all docs into an array in '$group' but it may not work for large datasets) */
db.collection.aggregate([
  {
    $facet: {
      data: [ { $match: {} } ], /** Get all docs without any filter */
      total: [
        {
          $group: { /** Group all docs & sum-up 'result' field */
            _id: "",
            Total: { $sum: "$response" }
          }
        }
      ]
    }
  },
  {
    $unwind: "$data"
  },
  {
    $unwind: "$total"
  },
  /** Merge 'total' field into 'data' & make data field as new root for documents */
  {
    $replaceRoot: { newRoot: { $mergeObjects: [ "$total", "$data" ] } }
  }
])

Test : MongoDB-Playground

Old : If Total is same value for all docs .

If it's the same value needed to be added across all documents in aggregation result then just use aggregation stage $addFields :

{ $addFields : { Total :5 } }

Upvotes: 2

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