MongoDB $addToSet replace - arrays

Question

I have a document like the following one:
{
_id: "00112233",
array: [
{
_id: "potatoes",
amount: 5
},
{
_id: "carrots",
amount: 6
}
]
}
and I need to update or push the documents so that if there is one in the array, it gets replaced, if not, it gets pushed.
If i try to do an update like this:
db.collection.update(
{ _id: "00112233" },
{
"$push": { "array": { "$each": [
{
_id: "potatoes",
amount: 6
},
{
_id: "apples",
amount: 2
}
]}}
}
)
In the database I will find two "potatoes" field. But if I try to replace the "push" with a "addToSet" I won't have the "potatoes" field updated.
Is there any way I can do this in only one query?

Answer 1

Unfortunately, you can't achieve the result that you are expecting in single update operation.
The addToSet doesn't work for this scenario because the array has embedded documents. addToSet checks for both the attribute names and values whether it matches. If match is found, it does nothing. If the match is not found, it adds the data to the array attribute.
In the above case for "potatoes", the amount value of potatoes doesn't match. So it inserts a new element into array. So the result has two potatoes with 2 different values.
{
_id: "potatoes",
amount: 6
}
You may need to perform two update operations.
1) Update the value of an array field if it exists using $set
db.collection.update(
{ _id: "00112233", "array._id": "potatoes"},
{
"$set": { "array.$":
{
_id: "potatoes",
amount: 7
}
},
}
);
2) Add the new element to an array field if it doesn't exists using $addToSet
db.collection.update(
{ _id: "00112233"},
{
"$addToSet": { "array":
{
_id: "apples",
amount: 7
}
},
}
);

Answer 2

you need to use $set instead of $push/$addToSet.
https://docs.mongodb.com/manual/reference/operator/update/set/

Answer 3

Had a similar issue and tried notion quest's approach and it did work.My schema was as follows
const MatchInstanceSchema = new Schema({
_id: false,
pseudoKey: { type: String, required: true, unique: true },
service: { type: String, required: true },
region: { type: String, required: true },
team1: {
name: { type: String, required: true },
price: { type: String, required: true }
},
team2: {
name: { type: String, required: true },
price: { type: String, required: true }
},
drawPrice: { type: String, required: true },
url: { type: String, required: true }
})
const MatchSchema = new Schema({
pseudoKey: { type: String, required: true, unique: true },
sport: { type: String, required: true },
league: { type: String, required: true },
date: { type: Date, required: true },
team1: { type: String, required: true },
team2: { type: String, required: true },
matchInstances: [MatchInstanceSchema]
})
I wanted to update the following matchInstances subdocument if there exists a match whose pseudoKey was same as the top level(parent document) pseudoKey without
duplicating the value and create a new entry in the matchInstances subdocument if it did not exist.
{
"_id" : ObjectId("5b47d47e7fd01d29178aa3a5"),
"pseudoKey" : "newcastle-tottenham",
"sport" : "Soccer",
"league" : "Premier League",
"date" : ISODate("2018-08-11T11:30:00.000Z"),
"team1" : "Newcastle",
"team2" : "Tottenham",
"matchInstances" : [
{
"team1" : {
"name" : "Newcastle",
"price" : "74.6"
},
"team2" : {
"name" : "Tottenham",
"price" : "2.06"
},
"pseudoKey" : "newcastle-tottenham",
"service" : "Betin",
"region" : "Kenya",
"drawPrice" : "3.45",
"url" : "https://web.betin.co.ke/Sport/SubEventOdds.aspx?SubEventID=16701401"
}
]
This was my solution
//If it already exists we just want to update with the new values without
//duplicating
Match.findOneAndUpdate(
{ pseudoKey: pseudoKey, "matchInstances.service": service },
{ $set: { "matchInstances.$": matchInstances[0] } }
//If it does not exist we want to add it as a new entry into the matchInstances
//subdocument
Match.findOneAndUpdate(
{ pseudoKey: pseudoKey },
{ $addToSet: { matchInstances: matchInstances } }
)