MongoDB Copy Database

Copying a database in MongoDB is useful for backups, migrations, or creating test environments. This guide explains how to copy a database using MongoDB Shell, mongodump and mongorestore, and Node.js (Mongoose).

1. Copy a Database Using MongoDB Shell

MongoDB does not have a built-in copyDatabase() function in modern versions. Instead, you must manually copy collections.

A. Open MongoDB Shell

Start the MongoDB shell:

mongosh

B. Select the Source Database

use sourceDB

C. Copy Each Collection to the Target Database

To copy the posts collection from sourceDB to targetDB:

db.posts.aggregate([{ $out: "targetDB.posts" }])

✅ Verify the copy:

use targetDB
show collections

✅ Output:

posts

The the posts collection has been copied to targetDB.

2. Copy a Database Using `mongodump` and `mongorestore`

This method exports the database and then restores it into a new one.

A. Dump (Export) the Source Database

mongodump --db=sourceDB --out=/backup/

✅ This creates a backup in /backup/sourceDB/.

B. Restore (Import) to a New Database

mongorestore --db=targetDB /backup/sourceDB/

✅ Verify the copy:

mongosh
use targetDB
show collections

✅ Expected Output:

posts
users
comments

3. Copy a Database Using Node.js (Mongoose)

A. Install Dependencies

npm install mongoose

B. Create a Script to Copy All Collections

Create copyDatabase.js:

const mongoose = require('mongoose');

const sourceDB = 'mongodb://127.0.0.1:27017/sourceDB';
const targetDB = 'mongodb://127.0.0.1:27017/targetDB';

async function copyCollections() {
    try {
        const srcConn = await mongoose.createConnection(sourceDB, { useNewUrlParser: true, useUnifiedTopology: true });
        const tgtConn = await mongoose.createConnection(targetDB, { useNewUrlParser: true, useUnifiedTopology: true });

        const collections = await srcConn.db.listCollections().toArray();
        
        for (let collection of collections) {
            const docs = await srcConn.db.collection(collection.name).find().toArray();
            if (docs.length) {
                await tgtConn.db.collection(collection.name).insertMany(docs);
                console.log(`✅ Copied collection: ${collection.name}`);
            }
        }

        srcConn.close();
        tgtConn.close();
        console.log("🎉 Database copy complete!");
    } catch (error) {
        console.error("❌ Error copying database:", error.message);
    }
}

copyCollections();

C. Run the Script

node copyDatabase.js

✅ Output:

✅ Copied collection: posts
✅ Copied collection: users
✅ Copied collection: comments
🎉 Database copy complete!

4. Summary

✔ Copied collections manually using MongoDB Shell ($out).
✔ Used mongodump and mongorestore for full database copying.
✔ Created a Node.js script to copy all collections programmatically.

5. Next Steps

🔹 Schedule automatic backups for better data safety.
🔹 Use authentication when copying databases between servers.
🔹 Optimize large database copies using indexes.

Would you like help setting up automated backups or cloud migrations? 🚀

Souy Soeng

MongoDB Copy Database