Clone a collection in MongoDB?

To clone a collection in MongoDB, use the forEach() method to iterate through documents and insert them into a new collection. This creates an exact copy with all documents and their _id values preserved.

Syntax

db.sourceCollection.find().forEach(function(doc) {
    db.targetCollection.insert(doc);
});

Sample Data

First, let's create a collection with sample documents ?

db.studentInformation.insertMany([
    {"StudentName": "Chris"},
    {"StudentName": "Robert"},
    {"StudentName": "James"}
]);

{
    "acknowledged": true,
    "insertedIds": [
        ObjectId("5c8bc15780f10143d8431e21"),
        ObjectId("5c8bc15e80f10143d8431e22"),
        ObjectId("5c8bc17380f10143d8431e23")
    ]
}

Display the original collection ?

db.studentInformation.find();

{ "_id": ObjectId("5c8bc15780f10143d8431e21"), "StudentName": "Chris" }
{ "_id": ObjectId("5c8bc15e80f10143d8431e22"), "StudentName": "Robert" }
{ "_id": ObjectId("5c8bc17380f10143d8431e23"), "StudentName": "James" }

Clone the Collection

Use forEach() to clone all documents to a new collection ?

db.studentInformation.find().forEach(function(doc) {
    db.studentInformationClone.insert(doc);
});

Verify the Clone

Check that the cloned collection contains identical documents ?

db.studentInformationClone.find();

{ "_id": ObjectId("5c8bc15780f10143d8431e21"), "StudentName": "Chris" }
{ "_id": ObjectId("5c8bc15e80f10143d8431e22"), "StudentName": "Robert" }
{ "_id": ObjectId("5c8bc17380f10143d8431e23"), "StudentName": "James" }

Verify both collections exist ?

show collections;

studentInformation
studentInformationClone

Key Points

• The forEach() method preserves original _id values in the cloned collection.
• Both collections will contain identical documents with the same ObjectIds.
• The target collection is created automatically if it doesn't exist.

Conclusion

Use find().forEach() with insert() to create an exact clone of a MongoDB collection. This method preserves all document fields and ObjectIds, creating a perfect duplicate collection.