Upsert many documents in MongoDB

To upsert many documents in MongoDB, use bulk operations with the upsert() option. This allows you to update multiple documents if they exist, or insert new ones if they don't match the query criteria.

Syntax

var bulk = db.collection.initializeUnorderedBulkOp();
bulk.find({queryCondition}).upsert().update({
    $setOnInsert: {fieldsForNewDocuments},
    $set: {fieldsToUpdate}
});
bulk.execute();

Sample Data

Let us create a collection with duplicate documents −

db.demo425.insertMany([
    {"Name": "Chris", "Age": 21},
    {"Name": "David", "Age": 23},
    {"Name": "Chris", "Age": 21},
    {"Name": "Chris", "Age": 21}
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5e74ee4fbbc41e36cc3cae6c"),
        ObjectId("5e74ee56bbc41e36cc3cae6d"),
        ObjectId("5e74ee57bbc41e36cc3cae6e"),
        ObjectId("5e74ee5cbbc41e36cc3cae6f")
    ]
}

Display all documents from the collection −

db.demo425.find();

{"_id": ObjectId("5e74ee4fbbc41e36cc3cae6c"), "Name": "Chris", "Age": 21}
{"_id": ObjectId("5e74ee56bbc41e36cc3cae6d"), "Name": "David", "Age": 23}
{"_id": ObjectId("5e74ee57bbc41e36cc3cae6e"), "Name": "Chris", "Age": 21}
{"_id": ObjectId("5e74ee5cbbc41e36cc3cae6f"), "Name": "Chris", "Age": 21}

Example: Upsert Multiple Documents

Update all documents with Name "Chris" to "Robert" using bulk upsert operation −

var bulk = db.demo425.initializeUnorderedBulkOp();
bulk.find({Name: "Chris"}).upsert().update({
    $setOnInsert: {id: 101},
    $set: {Name: "Robert", Age: 23}
});
bulk.execute();

BulkWriteResult({
    "writeErrors": [],
    "writeConcernErrors": [],
    "nInserted": 0,
    "nUpserted": 0,
    "nMatched": 3,
    "nModified": 3,
    "nRemoved": 0,
    "upserted": []
})

Verify Result

Display all documents to see the updated results −

db.demo425.find();

{"_id": ObjectId("5e74ee4fbbc41e36cc3cae6c"), "Name": "Robert", "Age": 23}
{"_id": ObjectId("5e74ee56bbc41e36cc3cae6d"), "Name": "David", "Age": 23}
{"_id": ObjectId("5e74ee57bbc41e36cc3cae6e"), "Name": "Robert", "Age": 23}
{"_id": ObjectId("5e74ee5cbbc41e36cc3cae6f"), "Name": "Robert", "Age": 23}

Key Points

• $setOnInsert sets values only when a new document is inserted (upserted)
• $set updates fields in both existing and newly inserted documents
• nMatched: 3 shows that 3 existing documents were found and updated
• nUpserted: 0 indicates no new documents were inserted in this case

Conclusion

Bulk upsert operations efficiently handle multiple document updates or inserts in a single operation. Use $setOnInsert for new document fields and $set for universal updates across all matching documents.