Field-symbols 和 Work area处理内表时性能分析

在ABAP Programming时，经常会遇到处理内表（如 appending & modifying）的记录，我们可以使用field-symbols，来减少处理的时间，提高程序性能。

因为field-symbols相当于C语言中的de-referenced指针，直接取内存中的值，不需要在开辟（work area）内存空间，move到此空间是需要花费时间的。

field-symbols performance测试案例：

1. DATA: i_bseg TYPE STANDARD TABLE OF bseg,
   
2.       wa_bseg LIKE LINE OF i_bseg.
   
3. *
   
4. DATA: lv_flag TYPE flag,
   
5.       lv_sta_time TYPE timestampl,
   
6.       lv_end_time TYPE timestampl,
   
7.       lv_diff_w   TYPE p DECIMALS 5,
   
8.       lv_diff_f   LIKE lv_diff_w,
   
9.       lv_save     LIKE lv_diff_w.
   
10. *
    
11. FIELD-SYMBOLS: <fs_bseg> LIKE LINE OF i_bseg.
    
12. *
    
13. * data selection = 10,000 records
    
14. SELECT * FROM bseg INTO TABLE i_bseg UP TO 10000 ROWS.
    
15. *
    
16. * Begin - Processing with Work area
    
17. GET TIME STAMP FIELD lv_sta_time.
    
18. LOOP AT i_bseg INTO wa_bseg.
    
19.   IF lv_flag = 'X'.
    
20.     wa_bseg-sgtxt = 'TEST'.
    
21.     MODIFY i_bseg FROM wa_bseg.
    
22.   ENDIF.
    
23.   CLEAR wa_bseg.
    
24.   IF lv_flag IS INITIAL.
    
25.     lv_flag = 'X'.
    
26.   ENDIF.
    
27. ENDLOOP.
    
28. GET TIME STAMP FIELD lv_end_time.
    
29. lv_diff_w = lv_end_time - lv_sta_time.
    
30. WRITE: /(15) 'Work area', lv_diff_w.
    
31. * End   - Processing with Work Area
    
32. *
    
33. CLEAR: lv_flag,
    
34.        lv_sta_time,
    
35.        lv_end_time.
    
36. * Begin - Processing with Field-Symbols
    
37. GET TIME STAMP FIELD lv_sta_time.
    
38. LOOP AT i_bseg ASSIGNING <fs_bseg>.
    
39.   IF lv_flag = 'X'.
    
40.     <fs_bseg>-sgtxt = 'TEST'.
    
41.   ENDIF.
    
42.   IF lv_flag IS INITIAL.
    
43.     lv_flag = 'X'.
    
44.   ENDIF.
    
45. ENDLOOP.
    
46. GET TIME STAMP FIELD lv_end_time.
    
47. lv_diff_f = lv_end_time - lv_sta_time.
    
48. WRITE: /(15) 'Field-Symbol', lv_diff_f.
    
49. * End   - Processing with Work Area
    
50. *
    
51. * Net time saving
    
52. lv_save = lv_diff_w - lv_diff_f.
    
53. WRITE: /(15) 'Total Save', lv_save.
    
54. WRITE: / 'Done'.

复制代码

测试结果：

由此可见field-symbols只花费原先Work area的1/5的时间