MongoDB GridFS Overview

What is GridFS?

• GridFS is a specification for storing and retrieving large files in MongoDB, such as images, videos, and documents.
• It allows the storage of files larger than the BSON-document size limit of 16MB.

Key Concepts

• File Storage: GridFS breaks files into smaller chunks (default size is 255KB) and stores them as documents in two collections:
  • fs.chunks: Contains the actual data chunks.
  • fs.files: Stores metadata about the files (like filename, upload date, etc.).
• Automatic Chunking: When a file is uploaded, GridFS automatically divides it into chunks, which can be stored independently.
• Metadata: You can store additional information about the file in the fs.files collection, such as:
  • Filename
  • Content type
  • Upload date

Benefits of Using GridFS

• Handles Large Files: Can store files of any size by breaking them into manageable pieces.
• Efficient Retrieval: Allows for efficient retrieval of file chunks, which can be streamed as needed.
• Metadata Support: Enables the storage of file-related information alongside the data.

Basic Operations

Uploading a File

Use the GridFS API or a driver to upload a file. Here’s an example in Node.js:

const { MongoClient, GridFSBucket } = require('mongodb');
const fs = require('fs');

async function uploadFile() {
    const client = new MongoClient('mongodb://localhost:27017');
    await client.connect();
    const db = client.db('test');
    const bucket = new GridFSBucket(db);
    
    const uploadStream = bucket.openUploadStream('myFile.txt');
    fs.createReadStream('./myFile.txt').pipe(uploadStream);
}

Downloading a File

To retrieve a file, use the GridFS API to read the data back into a stream:

async function downloadFile() {
    const client = new MongoClient('mongodb://localhost:27017');
    await client.connect();
    const db = client.db('test');
    const bucket = new GridFSBucket(db);
    
    const downloadStream = bucket.openDownloadStreamByName('myFile.txt');
    downloadStream.pipe(fs.createWriteStream('./downloadedFile.txt'));
}

Conclusion

• GridFS is a powerful tool for storing and managing large files in MongoDB.
• By understanding how it works, you can efficiently handle file uploads, downloads, and storage in your applications.