Google Summer of Code: question about GiST API advancement project

Hi, hackers,

I'm Rui Guo, a PhD student focusing on database at the University of
California, Irvine. I'm interested in the "GiST API advancement" project
for the Google Summer of Code 2019 which is listed at
https://wiki.postgresql.org/wiki/GSoC_2019#GiST_API_advancement_.282019.29 .

I'm still reading about RR*-tree, GiST and the PostgreSQL source code to
have a better idea on my proposal. Meanwhile, I have a very basic and
simple question:

Since the chooseSubtree() algorithm in both R*-tree and RR*-tree are
heuristic and somehow greedy (e.g. pick the MBB that needs to enlarge the
least), is it possible to apply *machine learning* algorithm to improve it?
The only related reference I got is to use deep learning in database join
operation (https://arxiv.org/abs/1808.03196) Is it not suitable to use
machine learning here or someone already did?

Thanks,
Rui Guo