帮我看看这个执行计划

EXPLAIN PLAN FOR SELECT * FROM (SELECT a.*,ROWNUM r FROM (SELECT sbbh,fxbh,clbh,hphm,hpzl,tztx,qjtx,jgsj FROM collect_af WHERE INSTR(hphm,'A')>0 ORDER BY jgsj DESC) a WHERE ROWNUM<=40) WHERE r>=1;
执行后结果：
PLAN_TABLE_OUTPUT                                                               
--------------------------------------------------------------------------------
Plan hash value: 4092853332                                                     
                                                                                
--------------------------------------------------------------------------------
-----------------------                                                         
                                                                                
| Id  | Operation                | Name       | Rows  | Bytes | Cost (%CPU)| Tim
e     | Pstart| Pstop |                                                         
                                                                                
--------------------------------------------------------------------------------
-----------------------                                                         
                                                                                
|   0 | SELECT STATEMENT         |            |    40 | 13040 |    39   (3)| 00:
00:01 |       |       |                                                         
                                                                                
|*  1 |  VIEW                    |            |    40 | 13040 |    39   (3)| 00:
00:01 |       |       |                                                         
                                                                                
|*  2 |   COUNT STOPKEY          |            |       |       |            |    
      |       |       |                                                         
                                                                                
|   3 |    VIEW                  |            |   254 | 79502 |    39   (3)| 00:PLAN_TABLE_OUTPUT                                                               
--------------------------------------------------------------------------------
00:01 |       |       |                                                         
                                                                                
|*  4 |     SORT ORDER BY STOPKEY|            |   254 | 55118 |    39   (3)| 00:
00:01 |       |       |                                                         
                                                                                
|   5 |      PARTITION RANGE ALL |            |   254 | 55118 |    38   (0)| 00:
00:01 |     1 |    20 |                                                         
                                                                                
|*  6 |       TABLE ACCESS FULL  | COLLECT_AF |   254 | 55118 |    38   (0)| 00:
00:01 |     1 |    20 |                                                         
                                                                                
--------------------------------------------------------------------------------
-----------------------          
在HPHM 和 CLBH上建立了索引；表中数据有2000多W条：
当查询条件包含号牌号码时，查询结果要90秒左右！ 各位大神有什么看法？