Show HN: I replaced vector databases with Git for AI memory (PoC) (github.com)

I'm no ai expert so consider my opinion having little value besides casual user. But I really like this. It seems clever and easy for me to grasp some pros for this approach.

I could envision a bunch of use cases about this workikg well. Ive personally encounter scenadios where sometimes the ai gets hung up on irrelevant outdated fact. But could still look up if specifically needed.

I could see even an automated short summary of all history that is outdated being updated in the vector db from this too. So not all context is lost.

Keep up the great work!

Seems really interesting! It would be great to see some evals to understand how well this works when stacked up against different approaches and use cases.

Using a vector db that’s created as a post commithook is probably a reasonable improvement. With context lengths getting bigger natural language is getting easier to work with but your leaving a bunch of gains on the floor without them.

No shade on your project, this is an emerging space and we can all use novel approaches.

Keep it up!

This is cool! Do you have any plans on releasing it as an MCP server? Would love to add this to my mcp gateway service https://mcp-boss.com/ (shameless plug)

I'm failing to grasp how it solves/replaces what vector db were created for in the first place (high-dimensional neighborhood searching, where the space to be searched grows by distance^dimension)

Interesting idea, I like the fact that it doesn't use embeddings, and going into historical memory is an extra step that doesn't impact the speed of resolving the current information

Just had a look at the repo -- I'm curious to know where this goes when you add vectors for semantic / hybrid search.

The use of commit-hooks is also very clever (mentioned here in the replies)

I mean these are two completely different approaches for completely different purposes. So saying that git replaces vector database is like saying that that a filing cabinet replaces a search engines.

I think BM25 is the right path for most use cases. I'd reach for a single lucene index here, making the commit hash one of the document's indexed fields. This would make FTS across history nearly instant. I'd store it in an ignored folder right next to .git.

For code search only, BM25 might be a bit overkill and not exactly what you want. FM indexes would be a simpler and faster way to implement pure substring search.

Maybe having both kinds of search at the same time could work better than either in isolation. You could frame them as "semantic" and "exact" search from the perspective of the LLM tool calls. The prompt could then say things like "for searching the codebase use FunctionA, for searching requirements or issues, use FunctionB."

I was working on memory consolidation and memory pruning 3 years ago (with GPT3 Davinci). Glad to see more people are working towards this.

Very interesting idea! I also replaced vector databases with "Table of Content" for retrieval: https://colab.research.google.com/github/VectifyAI/PageIndex...

Interesting! Text files in git can work for small sizes, like your 100MB.

That is what's known in FAISS as a "flat" index, just one thing after another. And obviously you can query by primary key to the key-value store that is git, and do atomic updates as you'd expect. In SQL land this is an unindexed column, you can do primary key lookups on the table, or you can look through every row in order to find what you want.

If you don't need fast query times, this could work great! You could also use SQL (maybe an AWS Aurora Postgres/MySQL table?) and stuff the fact and its embedding into a table, and get declarative relational queries (find me the closest 10 statements users A-J have made to embedding [0.1, 0.2, -0.1, ...] within the past day). Lots of SQL databases are getting embedding search (Postgres, sqlite, and more) so that will allow your embedding search to happen in a few milliseconds instead of a few seconds.

It could be worth sketching out how to use SQLite for your application, instead of using files on disk: SQLite was designed to be a better alternative to opening a file (what happens if power goes out while you are writing a file? what happens if you want to update two people's records, and not get caught mid-update by another web app process?) and is very well supported by many language ecosystems.

Then, to take full advantage of vector embedding engines: what happens if my embedding is 1024 dimensions and each one is a 32 bit floating point value? Do I need to save all of that precision? Is 16-bit okay? 8-bit floats? What about reducing the dimensionality? Is it good enough accuracy and recall if I represent each dimension with an index to a palette of the best 256 floats for that dimension? What about representing each pair of dimensions with an index to a palette of the best 256 pairs of floats for those two dimensions? What about, instead of looking through every embedding one by one, we know that people talk about one of three different topics, and we have three different indices for each of those major topics, and to find your nearest neighbors you want to first find your closest topic (or maybe closest two topics?) and then search in those lower indices? Each of these hypotheticals is literally a different “index string” in an embedding search called FAISS, and could easily be thousands of lines of code if you did it yourself.

It’s definitely a good learning experience to implement your own embedding database atop git! Especially if you run it in production! 100MB is small enough that anything reasonable is going to be fast.

You could use BM25S [0] instead of rank-bm25 for a nice speedup.

Also, there are tradeoffs associated with using BM25 instead of embedding similarity. You're essentially trading semantic understanding for computational speed and keyword matching.

[0] https://github.com/xhluca/bm25s

Maybe you can use Mercurial for this? You don’t need the complexity of Git for memory.

Hey Alex, we actually had a very similar idea this morning! I could not find your contact anywhere, would love to chat. This is really cool.

I'm also working on something in this space ("git-native memory for AI assistants"), with a completely different approach though. Will have my assistant check out your repo!

I think part of the reason i like Claude Code so much for non-technical organizational work, is that it's like a controllable memory with human in the loop (as well as a powerful general agent in the loop). Most of what i do is basically just doc creation and management. "Create this doc using this context and store it in this directory." In ChatGPT, I don't have much control or visibility over the memory.

Great idea! How does it compare to Graphiti / Zep? They use real time knowledge-graphs to tackle the problem you are trying to solve https://github.com/getzep/graphiti

Very nice. We tackled the temporal issue "versioned" in your case with a temporal knowledge graph: https://www.falkordb.com/blog/building-temporal-knowledge-gr...

Really cool work! This is something I’ve been interested in for a while, and I’m excited to try it out. Cheering you on!

Somehow i feel like the op doesn't get what vector DB's are actually for, semantic search isn't the same as a markdown memory file

I recently wrote a short anecdote in a similar vein- in my testing, “agentic” retrieval where you simply pass an annotated list of files to an LLM and ask it which ones it wants to look at is probably better than traditional RAG for small datasets (few hundreds of docs).

I found it was both much simpler and more accurate at the cost of marginally more time and tokens, compared to RAG on embedded chunks with a vector store.

Shameless plug- https://www.matthewnewton.com/blog/replacing-rag