cartodb-postgresql/test/CDB_GreatCircle.sql

select ST_AsText(CDB_GreatCircle(CDB_LatLng(55.8580,4.2590), CDB_LatLng(40.7127,74.0059)));
select ST_AsText(CDB_GreatCircle(CDB_LatLng(55.8580,4.2590), CDB_LatLng(40.7127,74.0059), 50000));