How to ignore tracking certain field when using change stream

Working with Data
1 
{
id: 139234234,
count: 12,
type: apple,
buyer: alex,
}

When the buyer got updated, I don’t want to receive the update information from changeStream, is it possible ignore some of the fields when using change stream?

2

The change stream watch accepts a pipeline filter as an argument, so you can do some thing like this:

db.collection.watch(
    [
        {
            $match: {
                operationType: "update",
                "updateDescription.updatedFields.buyer": {
                    $exists: false
                }
            }
        }
    ]
)
3

What if I want to ignore the field is buyer: [subdocument] , the updateDescription is:

 updateDescription: {
    updatedFields: {
      'buyer.2.name': "alex",
      'buyer.2.price': 1.4,
      'buyer.2.max': 12146,
      }}

I want to ignore all the update&remove related to the buyer field. Thank you.

4

Can you give an example of the documents and the updates occurring on them?

5

Document example:

id: 139234234,
count: 12,
type: apple,
buyer: [{name: "peter", price: 1.23, max: 129}, 
{"alex", price: 1.4, "max": 12146}]
}

Updates occurring on it:

db.updateMany({ id: 139234234 }, [
    {
      $set: {
        buyer: {
          $concatArrays: [
            {
              $filter: {
                input: "$buyer",
                cond: {
                    { $ne: ["$$this.name", "john"] },
                },
              },
            },
            [
              {
                name: "john",
                price: 12,
                max: 234,
              },
            ],
          ],
        },
      },
    },
  ]);
6

Is there anything you need from me? I want to ignore all updateFields that starting with buyer.

7

Are you wanting to ignore any updates that have buyer in them or are you wanting any update not to include buyer ?

8

I want any update not to include buyer, although I will not update/delete buyer with other field(both of them you mentioned will work for me in this case), I want to decrease the workload of change stream by not monitoring the buyer field from update and delete.

9

May I have any update in here, thank you.

10

This could be as simple as:

db.collection.watch(
    [
        {
            $project: {
                "updateDescription.updatedFields.buyer": 0
                }
          }
    ]
)
11

By applying your solution, I will also receive the above update.