Update single (same) field in every object of an array

[Prasad_Saya]

@Dan_Burt

How can I update all Array elements in this document? Each holeGross to be updated will [likely] be different, so need to match the hole.no (“elem.no”) against the corresponding new score.

Hello @Dan_Burt, you can use the Updates with Aggregation Pipeline feature to update different values of holeGross for all the elements of the holes array.

Suppose you have a document with two holes, for example:

{
        "_id" : 1,
        "player" : "John",
        "holes" : [
                {
                        "no" : 1,
                        "par" : 3,
                        "holeGross" : 2
                },
                {
                        "no" : 2,
                        "par" : 4,
                        "holeGross" : 3
                }
        ]
}

and the new values of hole gross in an array, for example:

var new_vals = [ 9, 5 ]

The following update operation will change each element of the array with new values (in your case, you need to supply an array of 8 elements as there are eight holes) in a single call.

db.collection.updateOne(
  { _id: 1 },
  [
    {
      $set: {
          holes: {
              $map: {
                  input: { $range: [ 0, { $size: "$holes" } ] },
                  in: {
                      $mergeObjects: [ 
                          { $arrayElemAt: [ "$holes", "$$this"  ] }, 
                          { holeGross: { $arrayElemAt: [ new_vals, "$$this"  ] } } 
                      ]
                  }
              }
          }
       }
    }
  ]
)