/**
* Gets the ID of the last pulled train update.
*
* @return the ID or -1 if there aren't any stored IDs.
*/
public static long getLatestUpdateId() {
StorageStats stats = getStorageStats();
if (stats != null) {
return stats.getLatestUpdateId();
}
// TODO: will stats ever be null?
// TODO: We should store the latest ID instead of querying for it.
// That way we don't run into a situation where the data store gets cleared and we end up
// pulling 200 updates.
// Attempt to just pull the value out of the cache.
// We assume that the latest updates will always live here.
@SuppressWarnings("unchecked")
List<TrainUpdate> cachedUpdates = (List<TrainUpdate>) cache.get(CACHED_UPDATES_KEY);
if (cachedUpdates != null && !cachedUpdates.isEmpty()) {
log.info("Fetched cache with size of : " + cachedUpdates.size());
return cachedUpdates.get(cachedUpdates.size() - 1).getTwitterId();
}
// If no cached updates were found, we must query the datastore.
long sinceId = -1;
PersistenceManager pm = PMF.get().getPersistenceManager();
try {
Query query = pm.newQuery(TrainUpdate.class);
query.setOrdering("date DESC");
query.setRange(0, 1);
@SuppressWarnings("unchecked")
List<TrainUpdate> oldUpdates = (List<TrainUpdate>) query.execute();
if (oldUpdates.size() > 0) {
sinceId = oldUpdates.get(0).getTwitterId();
}
} finally {
pm.close();
}
return sinceId;
}
