// call the 'migrate_up' or down method as appropriate,
// which every class of type Migration must support.
if (direction.equals("down")) {
logger.info("migrating down: " + mg);
res = mg.migrate_down(cursor, range, params);
cursor = res.get("cursor");
}
else {
logger.info("migrating up: " + mg);
res = mg.migrate_up(cursor, range, params);