MongoDB $setOnInsert Operator (original) (raw)

Last Updated : 12 Jul, 2025

The**$setOnInsert** operator in **MongoDB is a powerful tool used in updating operations with the **upsert**option. It allows us to specify values that should be set only when a new document is inserted. In this article, we will learn about the ****$setOnInsert Operator in MongoDB** in detail and so on.

MongoDB $setOnInsert Operator

**MongoDB ****$setOnInsert** Operator is a type of field **update MongoDB offers various array expression operators for use in the aggregation pipeline stages and arrayElemAtisonesuchoperator.TheMongoDB∗∗∗∗arrayElemAt is one such operator. TheMongoDB ****arrayElemAtisonesuchoperator.TheMongoDB∗∗∗∗setOnInsert** operator is used in MongoDB update operations with the upsert option.
When a new document is inserted, it assigns specified values to the fields in the document. This operator only acts during the insertion of a new document.
This operator can also work with embedded/nested documents. You can use this operator in methods like update(), findAndModify(), etc according to our requirements.
If the **update() or **findAndModify() method with **upsert: **true has found a matching document then MongoDB will ignore setOnInsertandapplythe∗∗setOnInsert and apply the setOnInsertandapplythe∗∗set operator.

**Syntax:

db.collection.update(
,
{ $setOnInsert: { : , : , ... } },
{ upsert: true }
)

Examples of MongoDB $setOnInsert Operator

In these examples, we will work with:

**Database: GeeksforGeeks

**Collection: Example

**Document: one documents that contain the details of the employees in the form of field-value pairs.

**Output:

demo database and collection example

Example 1: Upsert Results in an Insert

In this example, we are creating a new document in the Example collection with the help of update() method by setting the value of an upsert field to true and using $setOneInsert operator assign the values to the department and salary fields in the document.

**Query:

db.Example.update(
{
"name.first": "Mina",
"name.last": "Singh",
"personalDetails.age": 24,
"personalDetails.contactInfo": 345678901
},
{
$setOnInsert: { department: "Development", salary: 45000 }
},
{ upsert: true }
)

**Output:

example 1 output

Example 2: Inserting New Embedded Fields in New Document

In this example, we are creating a new document in the Example collection with the help of update() method by setting the value of an upsert field to true and using $setOneInsert operator assign the values to embedded fields i.e., in the document.

**Query:

db.Example.update(
{ "name.first": "Vinod", "experienceYear": 5 },
{
$setOnInsert: {
"personalDetails.age": 27,
"personalDetails.contactInfo": 345678901
}
},
{ upsert: true }
)

**Output:

example 2 output

Example 3: Effect of `$setOnInsert O`perator on Matched Documents

In this example, we are checking if setOnInsertoperatorworkwithmatcheddocumentornot.ThissetOnInsert operator work with matched document or not. This setOnInsertoperatorworkwithmatcheddocumentornot.ThissetOnInsert operator does not work with already present documents.

**Query:

db.Example.update(
{ "name.first": "Mina" },
{
$setOnInsert: {
"personalDetails.age": 27,
"personalDetails.contactInfo": 345678901
}
},
{ upsert: true }
)

**Before:

before collection

**Output After:

example 3 output

Key Takeaways About $setOnInsert Operator

The $setOnInsert operator in MongoDB is used to insert specific values during an upsert operation.
It does not affect existing documents or update operations that do not result in an insert.
The operator can also be used with embedded/nested documents using dot notation.
If an update operation finds a matching document, MongoDB will ignore the setOnInsertoperatorandapplythesetOnInsert operator and apply the setOnInsertoperatorandapplytheset operator instead.
The $setOnInsert operator is useful for setting default values or initializing fields only during the insertion of new documents.

Conclusion

The $setOnInsert operator in MongoDB provides a way to set specific values during an upsert operation, ensuring that these values are applied only when inserting new documents. This operator enhances the flexibility and functionality of MongoDB's update operations, making it easier to manage data in your collections.

MongoDB $setOnInsert Operator (original) (raw)