private boolean needsUpdate(long idxLastModified) {
   CollectionManager.ChangeChecker cc = GribIndex.getChangeChecker();
   for (CollectionManager dcm : collections) {
     for (MFile mfile : dcm.getFiles()) {
       if (cc.hasChangedSince(mfile, idxLastModified)) return true;
     }
   }
   return false;
 }