What is the function of the upsert option in MongoDB operations?

The upsert option in MongoDB operations serves the important function of inserting a new document if no documents match the specified query criteria. When you perform an update operation with the upsert option set to true, MongoDB first attempts to find a document that meets the query's criteria. If such a document is found, it gets updated with the new data specified in the update operation. Conversely, if no matching document exists, MongoDB will create a new document, incorporating the fields from the update statement as well as any fields specified in the query.

This feature is particularly useful in scenarios where you want to ensure that a document either exists (and is updated) or is created if it doesn’t. The use of upsert can help streamline the logic in your application by reducing the need to perform separate check-and-insert operations, allowing for a more efficient interaction with the database.

In this context, the other options do not capture the primary function of upsert. For instance, updating all matching documents is a standard behavior of the update operations regardless of the upsert option. Inspecting a document before making changes does not represent the upsert functionality, as upsert inherently focuses on adding a document if none are found. Additionally, creating a backup of a