Is it possible to implement find children/parent and spatial predicates with given geohash/H3 ?

I think the following functions can help some high level indexing for row / partition / file

st_geohash_children ( geohash_str , next_n_level)
st_geohash_parent ( geohash_str , previous_n_level)
st_geohash_contains ( geohash_str_large , geohash_str_small)
...

st_h3_children( h3_id, next_n_level)
st_h3_parent( h3_id, previous_n_level)
st_h3_contains( h3_id_large, h3_id_small)
...

No implementation files or tests are named. Start by locating the existing spatial SQL function entry points and reviewing how geohash and H3 values are represented; clarify the API and indexing scope before defining completion criteria for child, parent, and containment predicates.

Written by the indexing model from the issue text.