Update

Flexibility

• In MongoDB documents in a single collection can have different schemas
• Example: If a game does not have a poster field it may be excluded from the document completely. Other games in the collection may have it

updateOne()

• updateOne() takes filter as first argument, object with $set operator as second argument
• $set operator takes a document as argument which has one or more fields listed

updateOne(
    { filter }, {
        $set: {
            field: value
        }
    }
)

• filter may return multiple documents, but updateOne() updates the first result

updateOne(
    { title: "Uncharted" }, {
        $set: {
            poster: "https://example-posters.com/jIukjs901X891"
        }
    }
)

• If the document already has a poster field it is updated to new value
• If the document does not have a poster field, it is added
• Multiple fields can be updated at once

updateOne(
    { title: "Uncharted" }, {
        $set: {
            rating: 10,
            awards: {
                wins: 5,
                nominations: 10
            }
        }
    }
)

---

Update Operators

• Documentation

$set

• $set operator adds or replaces fields specified

$inc

• $inc increases the value by a specified amount

Before update

{
    title: "Uncharted",
    ign: {
        userReviews: 30,
        editorReviews: 1
    }
}

updateOne(
    { title: "Uncharted" }, {
        $inc: {
            "ign.userReviews": 40,
            "ign.editorReviews": 2
        }
    }
)

After update

{
    title: "Uncharted",
    ign: {
        userReviews: 70,
        editorReviews: 3
    }
}

---

Array Update Operators

$push

Before update

{
    title: "Uncharted",
    reviews: [
        {
            rating: 10,
            reviewer: "ign"
        }
    ]
}

updateOne(
    { title: "Uncharted" }, {
        $push: {
            reviews: {
                rating: 9.8,
                reviewer: "gamespot"
            }
        }
    }
)

After update

{
    title: "Uncharted",
    reviews: [
        {
            rating: 10,
            reviewer: "ign"
        },
        {
            rating: 9.8,
            reviewer: "gamespot"
        }
    ]
}

---

Modifiers

$each

• Modifies $push to append multiple items to array

updateOne(
    { title: "Uncharted" }, {
        $push: {
            reviews: {
                $each: [
                    {
                        rating: 9.8,
                        reviewer: "gamespot"
                    },
                    {
                        rating: 10,
                        reviewer: "metacritic"
                    }
                ]
            }
        }
    }
)

note

NOTE: If $each is not used in this case, entire reviews will be replaced by the array specified and the already existing elements will be erased

$sort

• Modifies the $push to reorder documents in array

updateOne(
    { title: "Uncharted" }, {
        $push: {
            reviews: {
                $each: [
                    {
                        rating: 9.8,
                        reviewer: "gamespot"
                    },
                    {
                        rating: 10,
                        reviewer: "metacritic"
                    }
                ],
                $sort: { rating: 1 }
            }
        }
    }
)

---

updateMany()

• Same as updateOne(). But instead updating the first resulting document, updateMany() updates all resulting documents

---

Upserts

• Use third argument as { upsert: true } to create a new document if it does not exist

db.games.updateOne(
    {
        title: "Horizon : Zero Dawn"
    },
    {
        $set: {
            _id: 30,
            platform: "PS4"
        }
    },
    {
        upsert: true
    }
)

---

replaceOne()

• Sytanx - replaceOne(filter, replacement_document)

let filter = { title : "Horizon : Zero Dawn"  }

let doc = db.games.findOne(filter);

doc.platform.push("PC");

db.games.replaceOne(filter, doc);

note

NOTE: Replacement document cannot contain update operators