was thinking about the option map that can contain a :builder-fn key

The builder only applies to the result set -- after the statement runs: if you aren't building a result set, builder function has no effect (which is why, in plan, if you take the optimized path and avoid building rows, the builder function is not invoked).

I see, thanks for the explanation Sean 🙂

This is described in the docs but if you have suggestions for making it clearer, let me know -- or open an issue with the suggestions.