Clone a collection in MongoDB?

To clone a collection in MongoDB, you can use the forEach() method. Let us first create a collection with a document.

The query to create a collection with a document is as follows −

> db.studentInformation.insertOne({"StudentName":"Chris"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5c8bc15780f10143d8431e21")
}
> db.studentInformation.insertOne({"StudentName":"Robert"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5c8bc15e80f10143d8431e22")
}
> db.studentInformation.insertOne({"StudentName":"James"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5c8bc17380f10143d8431e23")
}

Display all documents from a collection with the help of find() method. The query is as follows −

> db.studentInformation.find().pretty();

The following is the output −

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

Here is the query to make a clone in MongoDB −

> db.studentInformation.find().forEach( function(copyValue){db.makingStudentInformationClone.insert(copyValue)} );

Let us check the documents of clone collection in MongoDB. The query is as follows −

> db.makingStudentInformationClone.find();

The following is the output −

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

Let us now check the list of all collections including clone. The query is as follows −

> show collections;

The following is the output −

copyThisCollectionToSampleDatabaseDemo
deleteDocuments
deleteDocumentsDemo
deleteSomeInformation
employee
getElementWithMaxIdDemo
internalArraySizeDemo
makingStudentInformationClone
prettyDemo
selectWhereInDemo
sourceCollection
studentInformation
updateInformation
userInformation