How Document Versioning Works in MongoDB?

Document versioning in MongoDB is a powerful feature that allows developers to track changes to documents over time. It is particularly useful for applications that require auditing, historical analysis, or data integrity enforcement.

In this article, We will learn about How document versioning works in MongoDB by understanding in detail its types through examples.

Introduction to Document Versioning

• MongoDB supports document versioning, allowing users to track changes to documents over time.
  
• This feature is particularly useful for applications that require auditing, historical analysis, or data integrity enforcement.
  
• MongoDB typically implements document versioning using two approaches are defined as follows:

1. Embedded Versioning

• Embedded versioning in MongoDB is a technique where different versions of a document are stored within the document itself.
  
• Each document contains an array or nested structure to hold its historical versions.
  
• In embedded versioning, each document includes a field (e.g, versions) that stores an array of objects, with each object representing a version of the document.
  
• Each version object typically includes fields like version, timestamp and the actual document data in that version.

Example

Let's Implement a versioning system for user profiles in MongoDB to track changes over time and allow for historical analysis and data integrity enforcement.

{
  "_id": ObjectId("60c7d406d34e191174ca3e85"),
  "username": "john_doe",
  "email": "[email protected]",
  "profile": {
    "name": "John Doe",
    "age": 30
  },
  "versions": [
    {
      "version": 1,
      "username": "john_doe",
      "email": "[email protected]",
      "profile": {
        "name": "John Doe",
        "age": 30
      },
      "timestamp": ISODate("2024-05-10T12:00:00Z")
    },
    {
      "version": 2,
      "username": "john_doe",
      "email": "[email protected]",
      "profile": {
        "name": "John Doe",
        "age": 30,
        "location": "New York"
      },
      "timestamp": ISODate("2024-05-11T10:30:00Z")
    }
  ]
}

Explanation

• This MongoDB document stores a user profile with versioning. The main fields include _id, username, email and profile.
  
• The versions array contains sub-documents representing different versions of the profile, each with a version number, username, email, profile details and timestamp of the version.

2. External Versioning

• External Versioning in MongoDB refers to a method of managing document versions where historical versions of documents are stored in a separate collection or external system.
  
• In external versioning, historical versions of documents are stored in a separate collection from the original documents. This keeps the original documents clean and concise without the need to embed version history within them.
  
• External versioning often involves assigning a version number to each document version. This version number helps track the sequence of changes made to the document over time.
  
• External versioning is suitable for large documents or systems where managing multiple versions of documents efficiently is crucial.

Example

Let's create a query to solve the problem is to manage document versions for invoices in MongoDB and allowing for efficient tracking of changes and maintaining a history of modifications.

// invoices collection
{
    "_id": ObjectId("60c7d406d34e191174ca3e85"),
    "invoice_number": "INV-001",
    "total_amount": 100.00,
    "status": "paid",
    "last_updated": ISODate("2024-05-10T12:00:00Z"),
    "version_id": ObjectId("60c7d406d34e191174ca3e86") // the latest version
}

// invoice_versions collection
{
    "_id": ObjectId("60c7d406d34e191174ca3e86"),
    "invoice_id": ObjectId("60c7d40674ca3e85"), // Reference to the original invoice
    "version": 1,
    "fields": {
        "invoice_number": "INV-001",
        "total_amount": 100.00,
        "status": "pending"
    },
    "timestamp": ISODate("2024-05-10T12:00:00Z")
}

Explanation

• The code defines a schema for invoice documents in MongoDB. The "invoices" collection stores the latest version of each invoice, including fields like invoice_number, total_amount, status, last_updated, and a reference to the latest version in the "invoice_versions" collection.
  
• The "invoice_versions" collection stores historical versions of invoices each with a version number the fields that were changed and a timestamp indicating when the version was created. This approach enables tracking of changes and provides a history of modifications for each invoice.

Conclusion

Overall, Document versioning in MongoDB provides developers with the flexibility to choose between embedded and external versioning based on their application's requirements. Whether it's tracking changes to user profiles or managing versions of invoices. The MongoDB's document versioning features enable developers to implement robust and efficient version control mechanisms in their applications.