返回的结果集 遍历获取id查询效率太低
nutz可以用ids数组一次查询多条记录的嘛

				List<LuceneSearchResult> results = topicSearchService.search(search.trim(), 30);
				for (LuceneSearchResult result : results) {
					Topic topic = dao.fetch(Topic.class, result.getId());
					if (topic == null)
						continue;
					topics.add(topic);
				}