Unfortunately, I don't believe that it's possible to do this easily today because of the way bucket splits are handled. I wrote about this previously here, with an idea for solving the problem:
Thanks for alerting me to your previous idea. While I don't know enough about Postgresql internals to judge its merits yet, I'll write some pseudocode based on it in my proposal; and I'll relegate it to a "reach" proposal alongside a more straightforward one.
Tan
Hi Tan,
I'm not familiar with the inner workings of the GSoC, but I don't know if this can be relegated to a "stretch" goal. WAL logging is an all or nothing thing. I think that, to be applied to the codebase (which I assume is the goal of GSoC), all actions need to be implemented. That is probably why this has remained open so long: there is no incremental way to get the code written. (But I would like to see it get done, I don't want to discourage that.)