Refactoring random_file_index.
Refactoring random_file_index.

drolbr/Overpass-API,drolbr/Overpass-API,mmd-osm/Overpass-API,drolbr/Overpass-API,mmd-osm/Overpass-API,mmd-osm/Overpass-API,drolbr/Overpass-API,drolbr/Overpass-API,drolbr/Overpass-API,mmd-osm/Overpass-API