Index: lams_tool_survey/src/java/org/lamsfoundation/lams/tool/survey/dao/SurveyUserDAO.java
===================================================================
diff -u -rb7ba7cccd2f8027169900a05b8799d3287429c4e -r42358e1c2782a06507ed19dd6c3ec87ced01d8ac
--- lams_tool_survey/src/java/org/lamsfoundation/lams/tool/survey/dao/SurveyUserDAO.java	(.../SurveyUserDAO.java)	(revision b7ba7cccd2f8027169900a05b8799d3287429c4e)
+++ lams_tool_survey/src/java/org/lamsfoundation/lams/tool/survey/dao/SurveyUserDAO.java	(.../SurveyUserDAO.java)	(revision 42358e1c2782a06507ed19dd6c3ec87ced01d8ac)
@@ -40,4 +40,6 @@
     List<Object[]> getUsersForTablesorter(final Long sessionId, final Long questionId, int page, int size,
 	    int sorting, String searchString);
     int getCountUsersBySession(final Long sessionId, String searchString);
+    
+    public List<Object[]> getStatisticsBySession(final Long contentId);
 }
Index: lams_tool_survey/src/java/org/lamsfoundation/lams/tool/survey/dao/hibernate/SurveyUserDAOHibernate.java
===================================================================
diff -u -rb7ba7cccd2f8027169900a05b8799d3287429c4e -r42358e1c2782a06507ed19dd6c3ec87ced01d8ac
--- lams_tool_survey/src/java/org/lamsfoundation/lams/tool/survey/dao/hibernate/SurveyUserDAOHibernate.java	(.../SurveyUserDAOHibernate.java)	(revision b7ba7cccd2f8027169900a05b8799d3287429c4e)
+++ lams_tool_survey/src/java/org/lamsfoundation/lams/tool/survey/dao/hibernate/SurveyUserDAOHibernate.java	(.../SurveyUserDAOHibernate.java)	(revision 42358e1c2782a06507ed19dd6c3ec87ced01d8ac)
@@ -31,6 +31,7 @@
 import org.hibernate.SQLQuery;
 import org.lamsfoundation.lams.tool.survey.SurveyConstants;
 import org.lamsfoundation.lams.tool.survey.dao.SurveyUserDAO;
+import org.lamsfoundation.lams.tool.survey.model.SurveySession;
 import org.lamsfoundation.lams.tool.survey.model.SurveyUser;
 
 public class SurveyUserDAOHibernate extends BaseDAOHibernate implements SurveyUserDAO {
@@ -141,5 +142,21 @@
 	}
 	return ((Number) list.get(0)).intValue();
     }
+    
+    private static final String GET_STATISTICS = "SELECT session.*, COUNT(*) numUsers "
+		+ "  FROM tl_lasurv11_session session, tl_lasurv11_survey survey, tl_lasurv11_user user "
+		+ "  WHERE survey.content_id = :contentId and session.survey_uid = survey.uid  and user.session_uid = session.uid "
+		+ "  GROUP BY session.session_id";
+ 
+    @SuppressWarnings("unchecked")
+    /** Returns < [surveySession, numUsers] ...  [surveySession, numUsers]> */
+    public List<Object[]> getStatisticsBySession(final Long contentId) {
 
+	SQLQuery query = getSession().createSQLQuery(GET_STATISTICS);
+	query.addEntity(SurveySession.class)
+		.addScalar("numUsers", Hibernate.INTEGER)
+		.setLong("contentId", contentId);
+	return query.list();
+    }
+
 }
Index: lams_tool_survey/src/java/org/lamsfoundation/lams/tool/survey/service/SurveyServiceImpl.java
===================================================================
diff -u -rb7ba7cccd2f8027169900a05b8799d3287429c4e -r42358e1c2782a06507ed19dd6c3ec87ced01d8ac
--- lams_tool_survey/src/java/org/lamsfoundation/lams/tool/survey/service/SurveyServiceImpl.java	(.../SurveyServiceImpl.java)	(revision b7ba7cccd2f8027169900a05b8799d3287429c4e)
+++ lams_tool_survey/src/java/org/lamsfoundation/lams/tool/survey/service/SurveyServiceImpl.java	(.../SurveyServiceImpl.java)	(revision 42358e1c2782a06507ed19dd6c3ec87ced01d8ac)
@@ -439,16 +439,13 @@
     @Override
     public SortedMap<SurveySession, Integer> getStatistic(Long contentId) {
 	SortedMap<SurveySession, Integer> result = new TreeMap<SurveySession, Integer>(new SurveySessionComparator());
-	List<SurveySession> sessionList = surveySessionDao.getByContentId(contentId);
-	if (sessionList == null) {
-	    return result;
+	
+	List<Object[]> stats = surveyUserDao.getStatisticsBySession(contentId);
+	for ( Object[] stat : stats) {
+	    SurveySession session = (SurveySession) stat[0];
+	    Integer numUsers = (Integer) stat[1];
+	    result.put(session,numUsers);
 	}
-
-	for (SurveySession session : sessionList) {
-	    List<SurveyUser> users = getSessionUsers(session.getSessionId());
-	    result.put(session, users != null ? users.size() : 0);
-	}
-
 	return result;
 
     }