oracle强制执行索引

添加注释和取消的区别，F5查看效果，执行时间对比

SELECT COUNT(1)
  FROM (select *
          from vav_stbms_tb_act_source_2012
         where cstart_time >=
               to_date('2011/11/1 02:00:00', 'yyyy/mm/dd hh24:MI:ss')
           and cstart_time <
               to_date('2011/11/2 02:00:00', 'yyyy/mm/dd hh24:MI:ss')
           and creceivenetworkid = 2001
        UNION
        select /*+index(vav_stbms_tb_act_source_2012 VAV_SOURCE_INDEX2)*/
         *
          from vav_stbms_tb_act_source_2012
         where creceivedate >=
               to_date('2011/11/1 02:00:00', 'yyyy/mm/dd hh24:MI:ss')
           and creceivedate <
               to_date('2011/11/2 02:00:00', 'yyyy/mm/dd hh24:MI:ss')
           and creceivenetworkid = 2001)
/*cbo*/
/*rbo*/