I have solo built this:

https://github.com/bobjansen/Ibex

Ibex is a usable DSL for table manipulation that is quite fast

https://bobjansen.github.io/Ibex/benchmarks.html

I'm still managing to add more features, such as multithreading. The LLM's do make mistakes but they have gotten better and they tend to self correct these days. I'm also comparing results to mature products such as Polars and DuckDB and the results match.