Function duckdb_union_type_member_name 

pub unsafe extern "C" fn duckdb_union_type_member_name(
    type_: duckdb_logical_type,
    index: idx_t,
) -> *mut c_char

Retrieves the name of the union member.

The result must be freed with duckdb_free

type: The logical type object index: The child index returns: The name of the union member. Must be freed with duckdb_free.