I’ve been doing maintenance and bug fixes for this module for over 18 months now (last commit on HEAD seems to be mine), managing the last two releases. If you have questions and/or feedback, feel free.
Just wanted to say thank you! This extension was critical to a bunch of my research (and now my lab's research as well). Being able to control fine-grained elements of each plan while letting the PG planner "do the rest" has saved me personally probably 100s of hours of work.
I am digging into postgres source code past few weeks. This project seems like a good way to see how plugins integrate. I may reach out later if I have questions
There are many Postgres internals that people are usually not aware of, with more than one way to develop your module. I have a repo that’s a set of plugin templates here, that should be handy for your studies: https://github.com/michaelpq/pg_plugins