@Override
public Long2ObjectMap<UserHistory<Event>> get() {
Long2ObjectMap<List<Event>> table = new Long2ObjectOpenHashMap<List<Event>>();
Cursor<Event> events = eventDAO.streamEvents();
try {
for (Event evt : events) {
final long iid = evt.getUserId();
List<Event> list = table.get(iid);
if (list == null) {
list = Lists.newArrayList();
table.put(iid, list);
}
list.add(evt);
}
} finally {
events.close();
}
Long2ObjectMap<UserHistory<Event>> result =
new Long2ObjectOpenHashMap<UserHistory<Event>>(table.size());
for (Long2ObjectMap.Entry<List<Event>> evt : table.long2ObjectEntrySet()) {
long user = evt.getLongKey();
result.put(user, History.forUser(user, evt.getValue()));
evt.setValue(null);
}
return result;
}
/**
* Get a user's ratings.
*
* @param user The user ID.
* @return The ratings to retrieve.
*/
private SparseVector getUserRatingVector(long user) {
UserHistory<Rating> history = userEvents.getEventsForUser(user, Rating.class);
if (history == null) {
history = History.forUser(user);
}
return RatingVectorUserHistorySummarizer.makeRatingVector(history);
}
@Nullable
@Override
public ItemEventCollection<Event> apply(@Nullable Map.Entry<Long, List<Event>> input) {
if (input == null) {
return null;
} else {
return History.forItem(input.getKey(), input.getValue());
}
}