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Mongodb – Mongo DB Nested Array Updates & create in single mongo command

I have a nested mongo array

{
  "_id": 1,
  "date": "2024-09-30",
  "employees": [
    {
      "_id": 101,
      "name": "John Doe",
      "company": "ABC Corp",
      "department": "HR",
      "salary": 50000,
      "contactNumber": "123-456-7890"
    },
    {
      "_id": 102,
      "name": "A",
      "company": "XYZ Corp",
      "department": "HR",
      "salary": 500100,
      "contactNumber": "1333-456-7890"
    },
    {
      "_id": 103,
      "name": "B",
      "company": "XYZ Corp",
      "department": "HR",
      "salary": 500100,
      "contactNumber": "1333-456-7890"
    }
  ]
}

I need to update the salary of 101 and also add new memeber 104. How can i do in single update?

I am able to do with 2 updates. One to update 101’s salary using ArrayFilters and another is to $push 104 to array. Below are the queries,

db.collection.updateOne(
  { _id: 1 },  // Match the document with _id: 1
  {
    $set: { "employees.$[emp].salary": 60000 }  // Set the new salary for employee with _id: 101
  },
  {
    arrayFilters: [ { "emp._id": 101 } ]  // Array filter to target the specific employee with _id: 101
  }
)
db.collection.updateOne(
  { _id: 1 },  // Match the document with _id: 1
  {
    $push: {
      employees: {
        _id: 104,
        name: "New Employee",
        company: "New Corp",
        department: "HR",
        salary: 70000,
        contactNumber: "987-654-3210"
      }
    }
  }
)

Is there any way I can do both adding new employee and updating existing employee in same query.?

I think I can use aggregate to do so. but which is better in case of performance?

Tags:

2

Answers


  1. 0

    This can’t be be in a single update query – "Updating the path ’employees’ would create a conflict at ’employees’" – which happens because both operations are on the ’employees’ field. However, if you were pushing to a different field like newEmployees, then it would work. The only difference in those two linked queries is the field for $push.

    Anyway, wrt to doing both together with an aggregation, one agg would be faster than two separate updates but probably not worth the complexity. Does a new employee need to be added every time another employee’s salary changes?

    If you need "both work or both fail" behaviour, then consider using transactions.

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  2. 0

    You can do the followings in an update with aggregation pipeline.

    1. $concatArrays to append the new 104 entry to the end of the employees array
    2. $map to iterate through the resulting array. Conditionally update the array entry with $mergeObjects if the entry’s id is 101
    db.collection.update({
  "_id": 1
},
[
  {
    "$set": {
      "employees": {
        "$map": {
          "input": {
            "$concatArrays": [
              "$employees",
              [
                // new employee to insert here
                {
                  _id: 104,
                  name: "New Employee",
                  company: "New Corp",
                  department: "HR",
                  salary: 70000,
                  contactNumber: "987-654-3210"
                }
              ]
            ]
          },
          "as": "e",
          "in": {
            "$cond": {
              "if": {
                "$eq": [
                  101,
                  "$$e._id"
                ]
              },
              "then": {
                "$mergeObjects": [
                  "$$e",
                  {
                    // updates that you want to perform here
                    "salary": 60000
                  }
                ]
              },
              "else": "$$e"
            }
          }
        }
      }
    }
  }
])

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