MongoDB Update array element (document with a key) if exists, else push - mongodb

Question

I have such a schema:
doc:
{
//Some fields
visits:
[
{
userID: Int32
time: Int64
}
]
}
I want to first check if a specific userID exists, if not, push a document with that userID and system time, else just update time value. I know neither $push nor $addToSet are not able to do that. Also using $ with upsert:true doesn't work, because of official documentation advice which says DB will use $ as field name instead of operator when trying to upsert.
Please guide me about this. Thanks

Answer 1

You can use $addToSet to add an item to the array and $set to update an existing item in this array.
The following will add a new item to the array if the userID is not found in the array :
db.doc.update({
visits: {
"$not": {
"$elemMatch": {
"userID": 4
}
}
}
}, {
$addToSet: {
visits: {
"userID": 4,
"time": 1482607614
}
}
}, { multi: true });
The following will update the subdocument array item if it matches the userId :
db.doc.update({ "visits.userID": 2 }, {
$set: {
"visits.$.time": 1482607614
}
}, { multi: true });

Answer 2

const p = await Transaction.findOneAndUpdate(
{
_id: data.id,
'products.id': { $nin: [product.id] },
},
{
$inc: {
actualCost: product.mrp,
},
$push: {
products: { id: product.id },
},
},
{ new: true }
);
or
db.collection.aggregate([
{
"$match": {
"_id": 1
}
},
{
"$match": {
"sizes.id": {
"$nin": [
7
]
}
}
},
{
"$set": {
"price": 20
}
}
])
https://mongoplayground.net/p/BguFa6E9Tra

Answer 3

I know it's very late. But it may help others. Starting from mongo4.4, we can use $function to use a custom function to implement our own logic. Also, we can use the bulk operation to achieve this output.
Assuming the existing data is as below
{
"_id" : ObjectId("62de4e31daa9b8acd56656ba"),
"entrance" : "Entrance1",
"visits" : [
{
"userId" : 1,
"time" : 1658736074
},
{
"userId" : 2,
"time" : 1658736671
}
]
}
Solution 1: using custom function
db.visitors.updateMany(
{_id: ObjectId('62de4e31daa9b8acd56656ba')},
[
{
$set: {
visits: {
$function: {
lang: "js",
args: ["$visits"],
body: function(visits) {
let v = []
let input = {userId: 3, time: Math.floor(Date.now() / 1000)};
if(Array.isArray(visits)) {
v = visits.filter(x => x.userId != input.userId)
}
v.push(input)
return v;
}
}
}
}
}
]
)
In NodeJS, the function body should be enclosed with ` character
...
lang: 'js',
args: ["$visits"],
body: `function(visits) {
let v = []
let input = {userId: 3, time: Math.floor(Date.now() / 1000)};
if(Array.isArray(visits)) {
v = visits.filter(x => x.userId != input.userId)
}
v.push(input)
return v;
}`
...
Solution 2: Using bulk operation:
Please note that the time here will be in the ISODate
var bulkOp = db.visitors.initializeOrderedBulkOp()
bulkOp.find({ _id: ObjectId('62de4e31daa9b8acd56656ba') }).updateOne({$pull: { visits: { userId: 2 }} });
bulkOp.find({ _id: ObjectId('62de4e31daa9b8acd56656ba') }).updateOne({$push: {visits: {userId: 2, time: new Date()}}})
bulkOp.execute()
Reference link