How to use sort() in MongoDB update statements?

user_1535147 0
Viewed 117

I just want to update the top 2 highest fields in the database.

db.Employee.update({
    db.Employee.find().sort({
      Age: -1
    }).limit(2) --This part here wont work--
  },

  {
    $set: {
      Benefits: ["Vacation", "Rolex"]
    }
  }
)

Apparently MongoDB does not support such ability. How can I dynamically update the top 2 highest fields of my DB?

I do not want to resort to find the _id of the collection manually and then update the collection separately.

mongodb-query mongodb
2 Answers

Something simple like this can do the job:

db.Employee.find({}).sort({Age:-1}).limit(2).forEach(function(doc){
db.Employee.update({_id:doc._id},{$set:{Benefits:["Vacation","Rolex"]}})
})
user_104150470

Starting in MongoDB 4.4, there is a $merge stage in the aggregation that can allow updating the same collection with the aggregation results, so you can do something like this:

    db.Employee.aggregate([
  {
    $sort: {
      Age: -1
    }
  },
  {
    $limit: 2
  },
  {
    $set: {
      Benefits: [
        "Vacation",
        "Rolex"
      ]
    }
  },
  {
    $merge: {
      into: "Employee",
      on: "_id",
      whenMatched: "replace",
    }
  }
])

I tried it on my own db and it works, even though I could not make the playground update its own collection. The documentation for the $merge can be found here

user_184823100
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