Modify a document inside an array in MongoDB - mongodb

Question

Past answers (from mid 2013 and before) don't seem to work and links to the documentation are all out of date.
Example user object:
{
"name": "Joe Bloggs",
"email": "joebloggs#example.com",
"workstations" : [
{ "number" : "10001",
"nickname" : "home" },
{ "number" : "10002",
"nickname" : "work" },
{ "number" : "10003",
"nickname" : "vacation" }
]
}
How can I modify the nickname of a workstation?
I tried using $set, workstations.$ and workstations.nickname but none gave the desired results.

Answer 1

Short answer, you have to use array index. For example, you want to update the nickname of 10002: {$set:{"workstations.1.nickname":"newnickname"}}
Here is the complete example:
> db.test.update({"_id" : ObjectId("5332b7cf4761549fb7e1e72f")},{$set:{"workstations.1.nickname":"newnickname"}})
> db.test.findOne()
{
"_id" : ObjectId("5332b7cf4761549fb7e1e72f"),
"email" : "joebloggs#example.com",
"name" : "Joe Bloggs",
"workstations" : [
{
"number" : "10001",
"nickname" : "home"
},
{
"nickname" : "newnickname",
"number" : "10002"
},
{
"number" : "10003",
"nickname" : "vacation"
}
]
}
>
If you don't know the index (position of the workstations), you can update the doc using $elemMatch:
>db.test.update(
{
"email": "joebloggs#example.com",
"workstations": { "$elemMatch" { "number" : "10002" } }
},
{
"$set": { "workstations.$.nickname": "newnickname2" }
}
)
>

Answer 2

#naimdjon's answer would work. To generalize, you could use the $elemMatch operator in combination with the $ positional operator to update one element in the array using below query:
db.test.update({
// Find the document where name="Joe Bloggs" and the element in the workstations array where number = "10002"
"name": "Joe Bloggs",
"workstations":{$elemMatch:{"number":"10002"}}
},
{
// Update the nickname in the element matched
$set:{"workstations.$.nickname":"newnickname"}
})
Note: $elemMatch is only required if you need to match more than one component in the array. If you are going to match on just the number, you could use "workstations.number":"10002"

Answer 3

As long as you know "which" entry you wish to update then the positional $ operator can be of help. But you need to update your query form:
db.collection.update(
{
"email": "joebloggs#example.com",
"workstations": { "$elemMatch" { "nickname" : "work" } }
},
{
"$set": { "workstations.$.nickname": "new name" }
}
)
So that is the general form. What you need to do here is "match" something in the array in order to get a "position" to use for the update.
Alternately, where you know the position, then you can just "specify" the position with "dot notation":
db.collection.update(
{
"email": "joebloggs#example.com",
},
{
"$set": { "workstations.1.nickname": "new name" }
}
)
Which updates the second element in the array, and does not need the "matching" part in the query.