Git Internals: A Database Perspective

Developers use Git to collaborate on code: share code, work independently on local machines, and then combine efforts into a common repository. For many, this is done using very traditional steps and workflows that work really well in most cases. 

But what happens when you need to break the traditional model and do something new? Knowing more about Git internals will give you more power at your fingertips, especially as your project scales and you have to dive into more advanced features like indexes and query plans. 

Git is Your Engineering System’s Core Distributed Database

Git shares some very basic concepts with your application databases: 

1. Data is persisted to disk.
2. Queries allow users to request information based on that data.
3. The data storage is optimized for these queries.
4. The query algorithms are optimized to take advantage of these structures.
5. Distributed nodes need to synchronize and agree on some common state.

While these concepts are common to all databases, Git is particularly specialized because it was built to store plain-text source code files.

Git Objects

Git objects are arguably the most fundamental concepts in Git, acting like atoms of your Git repository that can be combined in interesting ways. 

Learn more about Git objects and how to use them. 

Git History Queries

Git plays a very important role in allowing developers to search and investigate the history of their repositories. When you start to think of Git as a database, these history investigations form an interesting query type. 

Git Commit History Queries 

Not only are history queries an interesting query type, but Git commit history presents interesting data shapes that inform how Git’s algorithms satisfy those queries.

Learn more about Git history queries based on commits. 

Git File History Queries 

Before making changes to a large software system, it’s critical to understand why the code is in its current state. Looking at Git commit messages alone is insufficient for finding changes that modified a specific file or certain lines in that file. Git’s file history commands help users find important points in time where changes were introduced.

Learn more about Git file history commands and how to use them. 

Download CTA: Searching through your project history, whether commit or file information, is easy and intuitive with GitKraken Client, giving you the visibility you need to truly understand your codebase. 

Distributed Synchronization in Git

The distributed nature of Git comes from its decentralized architecture. Each repository can act independently without connecting to a central server. Git uses several mechanisms to efficiently compute a small set of shareable objects without requiring a full list of objects on each side of the exchange. Doing so requires taking advantage of the object store’s shape, including commit history, tree walking, and custom data structures.

For most distributed systems, network partitions are supposed to be rare and short, even if unavoidable. With Git, partitions are the default state. Each user chooses when to synchronize information across these distributed copies. Even when they do connect, it can be only a partial update, such as when a user pushes one of their local branches to a remote.

With this idea of being disconnected by default, Git needs to consider its synchronization mechanisms differently than other databases. Each copy can have a very different state and each synchronization a different goal state.

Learn more about Git’s distributed synchronization. 

Scaling Your Database with Git

When a database approaches scale limits of a single database node, a common strategy is to shard the database by splitting it into multiple components. Similarly with Git, when a repository becomes too large, some choose to shard the repo. 

Learn about how to safely scale your Git database by sharing a Git repository and the factors you want to consider before getting started. 

Understanding Git Internals

Gaining a more comprehensive understanding of Git and how it works internally will yield significant benefits as you grow as a software developer. Using tools like GitKraken Client that increase the visibility of your project history can give you more confidence in your workflow and an intimate understanding of your code.