主题帖子数量不算在回复数之中

app/models/forum.rb

@@ -25,7 +25,7 @@ class Forum < ActiveRecord::Base
   def self.reset_counters!(forum_id)
     forum_id = forum_id.to_i
     update_all("topic_count = (SELECT COUNT(*) FROM #{Memo.table_name} WHERE forum_id=#{forum_id} AND parent_id IS NULL)," +
-     " memo_count = (SELECT COUNT(*) FROM #{Memo.table_name} WHERE forum_id=#{forum_id})," +
+     " memo_count = (SELECT COUNT(*) FROM #{Memo.table_name} WHERE forum_id=#{forum_id} AND parent_id IS NOT NULL)," +
      " last_memo_id = (SELECT MAX(id) FROM #{Memo.table_name} WHERE forum_id=#{forum_id})",
      ["id = ?", forum_id])
   end