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There are many ways in which users can clone a collection to the same MongoDB database or to another MongoDB database. This MongoDB tutorial article will discuss how users can copy/clone a database and its data in MongoDB.

Copy/clone a database in MongoDB using db.collection.copyTo() command

This command uses server-side JavaScript to copy all documents from a collection to newCollection. If the collection does not exist, MongoDB generates a new collection.

If permissions are enabled, you must perform all actions on all resources to run db.collection.copyTo(). If your business requires users to run db.collection.copyTo(), build a role that grants anyAction on anyResource.

No other users should be assigned this role.

Check field types when using db.collection.copyTo()to verify that the operation does not remove type information from the document during BSON to JSON conversion.

Internally, db.collection.copyTo()the method uses the eval command. Therefore, db.collection.copyTo()the operation takes a global lock, which prevents any other read or write activity until db.collection.copyTo()the operation is complete.

The number of documents copied is copyTo()returned by . If the copy fails, an exception is thrown. Because copyTo()uses eval internally, the copy operation on the mongod instance will block all other operations.

For example, the following operation copies all documents from the source collection to the target collection.

db.collection1.copyTo("collection2")

1. This command can only be run in MongoDB 4.0 or earlier.
2. It only clones the collection to the same database.
3. It is very slow.
4. It does not copy collection attributes and indexes.

Copy/clone a database in MongoDB using db.collection.find().forEach() command

This command iterates over the cursor, applying a JavaScript function to each document. The prototype of the forEach() method is as follows:

db.collection.find().forEach(<function>)

forEach()The method has the following parameters:

example:

db.collection1.find().forEach(
function(docs){
db.collection2.insert(docs);
})

1. This command can only clone a collection to the same server.
2. It is very slow.
3. It does not copy collection attributes and indexes.

Copy/clone a database in MongoDB using mongodump and mongorestore tools

To copy a database in earlier versions of MongoDB, you could use the copyDB command or its helper methods db.copyDatabase(). However, MongoDB has subsequently deprecated these.

Additionally, starting with version 4.2, MongoDB removed the copydb command and db.copyDatabase()method, so if you are using MongoDB 4.2 or later, you will not be able to use them. However, there is a different way to copy a MongoDB database.

MongoDB database tools can be used to clone a database in MongoDB. You can use the commands mongodump and mongorestore.

MongoDB Database Tools is a set of command-line tools for working with MongoDB. If you are not sure whether you have MongoDB Database Tools installed, check using a terminal or command prompt:

mongodump --version
mongorestore --version

This code basically finds the versions of mongodump and mongorestore. If you don't have them already, you can install the MongoDB database tools on your PC by following the installation instructions on the MongoDB website.

You must use your system's command line to run mongodump and mongorestore (for example, a new terminal or Command Prompt window). It should not be executed from the mongo shell.

Here is an example of database cloning code:

mongodump --archive --db=CatHotel | mongorestore --archive  --nsFrom='CatHotel.*' --nsTo='CatHouse.*'

In this case, we back up the CatHotel database and then restore all of its collections into a database called CatHouse. In other words, we clone the CatHotel database to CatHouse.

This uses mongodump to generate a database backup file, and then uses mongorestore to restore the database under a new name. First, the database is dumped to the standard output stream and piped into mongorestore.

Here's what each parameter does:

You can also dump all databases using mongodump and run it without any parameters. However, when you do this, the local and configuration databases are not included in the dump.

1. This is a high-speed method.
2. It can clone a collection to another database and server.

Copy/clone a database in MongoDB using mongoexport and mongoimport tools

The MongoDB Tools package includes the mongoexport and mongoimport tools. The tools package can be downloaded from the MongoDB Download Center.

For example, run the following command in the command line:

mongoexport.exe /host:<host> /port:<port> /db:test /collection:collection1 /out:collection1.json
mongoimport.exe /host:<host> /port:<port> /db:test /collection:collection2 /file:collection1.json

1. This is a quick method.
2. It can clone collections to different databases and servers.
3. It does not copy collection attributes and indexes.

Duplicate Collection Tool for NoSQL Manager for MongoDB

Duplicate Collections is a professional feature. It allows to copy collections very quickly in the same database.

Right-click the collection1 collection in the DB Explorer and select the Duplicate collection1 Collection item in the pop-up menu.

Specify the target collection name, copy parameters, and click Copy.

1. This is a high-speed method.
2. It copies the collection attributes and indexes.
3. It can only clone collections to the same database.

Another database tool to copy collections to NoSQL Manager for MongoDB

Copying a collection to another database is a professional feature of NoSQL Manager for MongoDB Pro. It allows copying one or more collections between databases and servers.

Right-click collection1 in the DB Explorer and select the Copy collection1 Collection to another Database item from the pop-up menu.

Specify the target database and other parameters and click Execute.

1. This is a quick method.
2. It copies the collection attributes and indexes.
3. It can replicate collections to another database and server.
4. It can copy multiple collections at once.
5. It cannot rename the collection.