How to add a new field to all documents in MongoDB Collection?

Add a new field to all documents in MongoDB Collection

To add a new field to every document in a MongoDB collection, you can use the updateMany() method with the $set operator. This operation is useful when you need to add the same field to multiple documents across a collection. The $set operator is efficient and straightforward, making it ideal for adding new fields in bulk updates.

Description:

In MongoDB, you can add a new field to all documents within a collection using the updateMany() method with the $set operator. This allows you to add the same field with a specified value to every document in a collection, without manually updating each document. This technique is particularly useful for schema evolution, where you need to add fields to all documents as your data structure evolves.

Syntax:

The syntax to add a new field to every document in a collection is:

db.<collection>.updateMany(
  {},                       // Empty filter to select all documents
  { $set: { <new_field>: <value> } }
)

Explanation:

• <collection>: The collection where documents will be updated.
• <new_field>: The name of the new field to add to each document.
• <value>: The value to assign to the new field.

Example:

Suppose you have a users collection and you want to add a new field called status with a value of "active" to every document in the collection. Here's how to do it:

Code:

// Add a new field 'status' with the value 'active' to every document in the users collection
db.users.updateMany(
  {},                        // Empty filter to select all documents
  { $set: { status: "active" } } // Set 'status' field to 'active'
)

Explanation:

• db.users.updateMany(...)
  The updateMany method is called on the users collection to update multiple documents at once.
• {}
  An empty filter {} is provided to select all documents within the collection. This ensures that every document is updated.
• { $set: { status: "active" } }
  The $set operator is used to add a new field. Here, it adds a field named status with the value "active" to each document. If status already exists in a document, its value will be updated to "active".

By running this command, all documents in the users collection will now have a status field with the value "active". This approach allows you to efficiently add or update fields in bulk without manually modifying each document.