// called by tdm
 public static boolean update(TimePartitionCollection tpc, Formatter f) throws IOException {
   Grib1TimePartitionBuilder builder =
       new Grib1TimePartitionBuilder(tpc.getCollectionName(), new File(tpc.getRoot()), tpc);
   if (!builder.needsUpdate()) return false;
   builder.readOrCreateIndex(CollectionManager.Force.always, f);
   builder.gc.close();
   return true;
 }