How to update field in array if specific field exists

Question

I have the following code for now :

ids = ["user1", "user2"]
item = {"uid": "12345", "name": "test"}

users_collection.update_many({"_id": {"$in": ids}}, {"$pull": {"users": {"uid": item["uid"]}}})
users_collection.update_many({"_id": {"$in": ids}}, {"$addToSet": {"users": item}}, upsert=True)

I am trying to maintain an array users with items with unique uids.

I would like ideally to replace the item if it's already in the array (by uid) to avoid pulling and re adding the item to the array. To recap :

Replace the item if uid exists in the array for one of the item
Add it if the item doesn't exists (knowing it by uid)

How can i achieve this in one query without aggregation ? Is it even possible ?

PS : Here is more or less what i want :

users_collection.update_many({"_id": {"$in": ids}}, {"$update": {"users": {"$where": {"$exists": "uid"} || {"uid": item["uid"]}, item}}}}, upsert=True)

Thanks in advance

ray · Accepted Answer · 2023-02-12 17:58:34Z

2

Use $map to iterate through the array and $cond to conditionally update the array entry with $mergeObject.

db.collection.update({
  _id: {
    $in: [
      "user1",
      "user2"
    ]
  }
},
[
  {
    "$set": {
      "items": {
        "$map": {
          "input": "$items",
          "as": "i",
          "in": {
            "$cond": {
              "if": {
                $eq: [
                  "$$i.uid",
                  "12345"
                ]
              },
              "then": {
                "$mergeObjects": [
                  "$$i",
                  {
                    "uid": "12345",
                    "name": "test"
                  }
                ]
              },
              "else": "$$i"
            }
          }
        }
      }
    }
  }
],
{
  multi: true
})

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answered Feb 12, 2023 at 17:58

ray

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