Bruno Roustant

Thank you for creating this issue. This is indeed a subject I'm interested in, although currently I'm on another learned algorithm to search sorted keys. This learned sort would be...

Fyi @antogruz and I are going to help on this PR. We'll first review and then propose new commits to fix tests.

When fields are sorted on numeric values, it could be possible to use a learned-index approach instead of raw binary search, something like the [PGM Index](https://github.com/carrotsearch/hppc/blob/master/hppc/src/main/templates/com/carrotsearch/hppc/KTypePgmIndex.java). It is very compact...