Crafting an Extension Framework for MySQL: a talk from MySQL BR Conf 2026

I opened my MySQL BR Conf 2026 talk creating a new data type that stock MySQL doesn’t have: ROT13. … OK, admittedly, it’s a silly type. With a ROT13 column, you insert plain strings and read back plain strings, but the table stores scrambled text. … OK, it’s very *very* silly. But the point of this example isn’t to convince you extensions are useful; it’s to show a tiny extension that allows exploring design choices we made in designing the VEF (VillageSQL Extension Framework).

What the talk covers

• Simpler functions and aggregates. VDF’s (VEF-Defined Functions) resemble MySQL UDF’s (User-Defined Functions), but are easier to write. I explore how we made it both more ergonomic in C++ and also how we make it harder to mess up.
• Types that take parameters. Some types take parameters; e.g., vectors need a length. To show how to handle this in our existing silly example, I generalize ROT13 into ROT(K).
• The escape path. I show how functions that don’t have tidy, compile-time signatures like printf fit into the VEF. I also describe our design pattern for cases like these. In the talk, I link to a blog post on this blog, which I will also now link here in an example of Linkception: “Happy Path, Escape Hatch, and the Space Between”.
• Porting a PostgreSQL extension. The talk ends with what happened when VillageSQL's Claude Code skill ported PostgreSQL's hstore extension, and what the port cost.

About Daniel Bentley

Dan is a founding engineer at VillageSQL. He has worked at Google and Twitter, and he did a startup called Tilt that focused on Kubernetes developer tools. He is on a quest to make databases delightful to use by translating complex systems into elegant simplicity.

Get started at villagesql.com, read the docs, or talk to us on Discord.