MongoDB Update Item in Array inside Array

Question

I want to update an existing item inside of an array in an array.

The structure of my document looks like the following:

    {
  "_id":"a1",
  "projects":[{
    "_id": "b1",
    "title":"Title A",
    "task":[
           {"_id": "c1",
            "title":"Title B"},
            {"_id": "c2",
            "title":"Title C"},
            {"_id": "c3",
            "title":"Title D"}
          ],

}]
}

Let's say we want to change the "task":

{"_id": "c2",
 "title":"Title C"}

to

{"_id": "c2",
 "title":"Title C1"}

Does someone know a proper way to update this subdocument?

Answer 1

By using a combination of $set with the posititonal operator and arrayFilters , this should be doable:

db.getCollection('so-test').updateOne(
   { _id: "a1"},
   { $set: { "projects.$[].task.$[task].title": "Title C1" } },
   { arrayFilters: [  {"task.title": "Title C"} ]}
)