CODEWITHSUNDEEP
mongodbupdates
徐巧民
徐巧民

Reputation: 593

MongoDB - Update an object in nested Array

{
  "_id": "xPBc4By8FemDwTPqH",
  "u": {
    "_id": "6PoZawHZcQz4Gwzcv",
    "username": "michael"
  },
  "friends": [
    {
      "u": {
        "_id": "eGqDjAjjtYADbuSnn",
        "username": "michael",
        "name": "michael"
      }
    },
    {
      "u": {
        "_id": "k4gKCGwYryXDMMHvs",
        "username": "joyce",
        "name": "joyce"
      }
    }
  ]
}

I want to update the name of "friends.u.username": "michael" 's name is "hello", how I need to do it.

Upvotes: 59

Views: 84995

Answers (4)

chridam
chridam

Reputation: 103305

Apply the $set operator together with the $ positional operator in your update to change the name field.

The $ positional operator will identify the correct element in the array to update without explicitly specifying the position of the element in the array, thus your final update statement should look like:

db.collection.update(
    { "friends.u.username": "michael" }, 
    { "$set": { "friends.$.u.name": "hello" } }
)

To update multiple elements in an array when more than one element matches the filter, you can use the $\[<identifier>\] syntax with the arrayFilters option. The following will update all matching elements in the "friends" array:

db.collection.update(
    { "friends.u.username": "michael" },
    { "$set": { "friends.$[elem].u.name": "hello" } },
    { 
      "arrayFilters": [{ "elem.u.username": "michael" }], 
      "multi": true 
    }
)

The $[elem] syntax identifies array elements that match the specified filter in the arrayFilters option. The multi: true option is added to update all matching documents instead of just the first one.

Upvotes: 113

Marcos Viana
Marcos Viana

Reputation: 161

If you are using python, I created this function to generate the new update:

def generate_set_to_update_document(field: str, changes: dict) -> dict:
    new_set = {}
    for change in changes.keys():
        new_set[f"{field}.$.{change}"] = changes[change]
    return new_set

Upvotes: 0

Sanjay Bharwani
Sanjay Bharwani

Reputation: 4739

Below should work fine as its tested

First check the current value of the array.

db.test.findOne({"friends.u.id" : "eGqDjAjjtYADbuSnn"},{"friends.u.name":1})

Now fire the update command

db.test.update({"friends.u.id" : "eGqDjAjjtYADbuSnn"},{$set:{"friends.$.u.name":"hello"}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

Now check the results again to validate the update values

db.test.findOne({"friends.u.id" : "eGqDjAjjtYADbuSnn"},{"friends.u.name":1})

Hope this helps.

Upvotes: 0

Srivatsa N
Srivatsa N

Reputation: 2321

You can use $set operator. 

> db.test.update({"friends.u._id":"eGqDjAjjtYADbuSnn"},{$set:{"friends.$.u.name":"hello"}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

Upvotes: 8

Related Questions