SAP ABAP的效率问题与代码优化的小思考

早上老白突然问个无聊的问题：将一个数取反，怎么写速度最快？

进而引发了一群人的探讨：

测试代码：

REPORT z_barry_test NO STANDARD PAGE HEADING.

DATA: t1 TYPE i,
      t2 TYPE i,
      pp TYPE p .

pp = '123456.78'.

GET RUN TIME FIELD t1.
DO 1000000 TIMES.
  pp = - pp .
ENDDO.
GET RUN TIME FIELD t2.
t1 = t2 - t1.
WRITE : / '  -  :' ,t1.

GET RUN TIME FIELD t1.
DO 1000000 TIMES.
  pp = 0 - pp .
ENDDO.
GET RUN TIME FIELD t2.
t1 = t2 - t1.
WRITE : / '0 -  :' ,t1.

GET RUN TIME FIELD t1.
DO 1000000 TIMES.
  pp = pp * -1 .
ENDDO.
GET RUN TIME FIELD t2.
t1 = t2 - t1.
WRITE : / '* -1 :' , t1.

REPORT z_barry_test NO STANDARD PAGE HEADING.

DATA: t1 TYPE i,

t2 TYPE i,

pp TYPE p .

pp = '123456.78'.

GET RUN TIME FIELD t1.

DO 1000000 TIMES.

pp = - pp .

ENDDO.

GET RUN TIME FIELD t2.

t1 = t2 - t1.

WRITE : / ' - :' ,t1.

GET RUN TIME FIELD t1.

DO 1000000 TIMES.

pp = 0 - pp .

ENDDO.

GET RUN TIME FIELD t2.

t1 = t2 - t1.

WRITE : / '0 - :' ,t1.

GET RUN TIME FIELD t1.

DO 1000000 TIMES.

pp = pp * -1 .

ENDDO.

GET RUN TIME FIELD t2.

t1 = t2 - t1.

WRITE : / '* -1 :' , t1.

下面代码是测试内表取值速度的：

REPORT z_barry_test NO STANDARD PAGE HEADING.

DATA: BEGIN OF itab OCCURS 0 ,
        ebeln LIKE ekko-ebeln,
        ebelp LIKE ekpo-ebelp,
        matnr LIKE ekpo-matnr,
      END OF itab.
DATA: BEGIN OF item OCCURS 0 ,
        ebelp LIKE ekpo-ebelp,
        matnr LIKE ekpo-matnr,
      END OF item.
DATA: BEGIN OF header OCCURS 0 ,
        ebeln LIKE ekko-ebeln,
        items LIKE item[],
      END OF header.
DATA: hs_header LIKE HASHED TABLE OF header
          WITH UNIQUE KEY ebeln WITH HEADER LINE.

DATA: BEGIN OF it_out OCCURS 0 ,
        ebeln LIKE ekko-ebeln,
        lines(100),
      END OF it_out.
DATA: itab2 LIKE itab[] WITH HEADER LINE.
DATA: t1 TYPE i,
      t2 TYPE i.

START-OF-SELECTION.
  SELECT ekko~ebeln
         ekpo~ebelp
         ekpo~matnr
    INTO TABLE itab
    FROM ekko INNER JOIN ekpo ON ekko~ebeln = ekpo~ebeln
    UP TO 30000 ROWS.

  GET RUN TIME FIELD t1.
  itab2[] = itab[].
  SORT itab2 BY ebeln.
  DELETE ADJACENT DUPLICATES FROM itab2 COMPARING ebeln.

  LOOP AT itab2.
    CLEAR it_out.
    LOOP AT itab WHERE ebeln = itab2-ebeln.
      CONCATENATE it_out-lines ',' itab-ebelp INTO it_out-lines.
    ENDLOOP.
    it_out-ebeln = itab2-ebeln.
    APPEND it_out.
  ENDLOOP.
  GET RUN TIME FIELD t2.
  t1 = t2 - t1.
  WRITE t1.

****优化算法
  DATA: tabix LIKE sy-tabix.
  CLEAR it_out[].
  SORT itab BY ebeln ebelp.
  itab2[] = itab[].
  DELETE ADJACENT DUPLICATES FROM itab2 COMPARING ebeln.

  GET RUN TIME FIELD t1.
  LOOP AT itab2.
    CLEAR it_out.
    READ TABLE itab WITH KEY ebeln = itab2-ebeln BINARY SEARCH.
    IF sy-subrc = 0.
      tabix = sy-tabix.
      LOOP AT itab FROM tabix WHERE ebeln = itab2-ebeln.
        CONCATENATE it_out-lines ',' itab-ebelp INTO it_out-lines.
      ENDLOOP.
    ENDIF.
    it_out-ebeln = itab2-ebeln.
    APPEND it_out.
  ENDLOOP.
  GET RUN TIME FIELD t2.
  t1 = t2 - t1.
  WRITE / t1.


****继续优化算法
  CLEAR it_out[].
  SORT itab BY ebeln ebelp.
  itab2[] = itab[].
  DELETE ADJACENT DUPLICATES FROM itab2 COMPARING ebeln.

  GET RUN TIME FIELD t1.
  LOOP AT itab2.
    CLEAR it_out.
    READ TABLE itab WITH KEY ebeln = itab2-ebeln BINARY SEARCH.
    IF sy-subrc = 0.
      tabix = sy-tabix.
      LOOP AT itab FROM tabix.
        IF itab-ebeln <> itab2-ebeln.
          EXIT.
        ENDIF.
        CONCATENATE it_out-lines ',' itab-ebelp INTO it_out-lines.
      ENDLOOP.
    ENDIF.
    it_out-ebeln = itab2-ebeln.
    APPEND it_out.
  ENDLOOP.
  GET RUN TIME FIELD t2.
  t1 = t2 - t1.
  WRITE / t1.


****深层哈希表，
  CLEAR it_out[].
  GET RUN TIME FIELD t1.
  LOOP AT itab.
    CLEAR hs_header.
    READ TABLE hs_header WITH TABLE KEY ebeln = itab-ebeln.
    IF sy-subrc = 0.
      MOVE-CORRESPONDING itab TO item.
      APPEND item TO hs_header-items.
      MODIFY TABLE hs_header.
    ELSE.
      MOVE-CORRESPONDING itab TO hs_header.
      MOVE-CORRESPONDING itab TO item.
      APPEND item TO hs_header-items.
      INSERT table hs_header.
    ENDIF.
  ENDLOOP.

  LOOP AT hs_header.
    CLEAR it_out.
    it_out-ebeln = hs_header-ebeln.
    LOOP AT hs_header-items INTO item.
      CONCATENATE it_out-lines ',' item-ebelp INTO it_out-lines.
    ENDLOOP.
    APPEND it_out.
  ENDLOOP.
  GET RUN TIME FIELD t2.
  t1 = t2 - t1.
  WRITE / t1.

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REPORT z_barry_test NO STANDARD PAGE HEADING.

DATA: BEGIN OF itab OCCURS 0 ,

ebeln LIKE ekko-ebeln,

ebelp LIKE ekpo-ebelp,

matnr LIKE ekpo-matnr,

END OF itab.

DATA: BEGIN OF item OCCURS 0 ,

ebelp LIKE ekpo-ebelp,

matnr LIKE ekpo-matnr,

END OF item.

DATA: BEGIN OF header OCCURS 0 ,

ebeln LIKE ekko-ebeln,

items LIKE item[],

END OF header.

DATA: hs_header LIKE HASHED TABLE OF header

WITH UNIQUE KEY ebeln WITH HEADER LINE.

DATA: BEGIN OF it_out OCCURS 0 ,

ebeln LIKE ekko-ebeln,

lines(100),

END OF it_out.

DATA: itab2 LIKE itab[] WITH HEADER LINE.

DATA: t1 TYPE i,

t2 TYPE i.

START-OF-SELECTION.

SELECT ekko~ebeln

ekpo~ebelp

ekpo~matnr

INTO TABLE itab

FROM ekko INNER JOIN ekpo ON ekko~ebeln = ekpo~ebeln

UP TO 30000 ROWS.

GET RUN TIME FIELD t1.

itab2[] = itab[].

SORT itab2 BY ebeln.

DELETE ADJACENT DUPLICATES FROM itab2 COMPARING ebeln.

LOOP AT itab2.

CLEAR it_out.

LOOP AT itab WHERE ebeln = itab2-ebeln.

CONCATENATE it_out-lines ',' itab-ebelp INTO it_out-lines.

ENDLOOP.

it_out-ebeln = itab2-ebeln.

APPEND it_out.

ENDLOOP.

GET RUN TIME FIELD t2.

t1 = t2 - t1.

WRITE t1.

****优化算法

DATA: tabix LIKE sy-tabix.

CLEAR it_out[].

SORT itab BY ebeln ebelp.

itab2[] = itab[].

DELETE ADJACENT DUPLICATES FROM itab2 COMPARING ebeln.

GET RUN TIME FIELD t1.

LOOP AT itab2.

CLEAR it_out.

READ TABLE itab WITH KEY ebeln = itab2-ebeln BINARY SEARCH.

IF sy-subrc = 0.

tabix = sy-tabix.

LOOP AT itab FROM tabix WHERE ebeln = itab2-ebeln.

CONCATENATE it_out-lines ',' itab-ebelp INTO it_out-lines.

ENDLOOP.

ENDIF.

it_out-ebeln = itab2-ebeln.

APPEND it_out.

ENDLOOP.

GET RUN TIME FIELD t2.

t1 = t2 - t1.

WRITE / t1.

****继续优化算法

CLEAR it_out[].

SORT itab BY ebeln ebelp.

itab2[] = itab[].

DELETE ADJACENT DUPLICATES FROM itab2 COMPARING ebeln.

GET RUN TIME FIELD t1.

LOOP AT itab2.

CLEAR it_out.

READ TABLE itab WITH KEY ebeln = itab2-ebeln BINARY SEARCH.

IF sy-subrc = 0.

tabix = sy-tabix.

LOOP AT itab FROM tabix.

IF itab-ebeln <> itab2-ebeln.

EXIT.

ENDIF.

CONCATENATE it_out-lines ',' itab-ebelp INTO it_out-lines.

ENDLOOP.

ENDIF.

it_out-ebeln = itab2-ebeln.

APPEND it_out.

ENDLOOP.

GET RUN TIME FIELD t2.

t1 = t2 - t1.

WRITE / t1.

****深层哈希表，

CLEAR it_out[].

GET RUN TIME FIELD t1.

LOOP AT itab.

CLEAR hs_header.

READ TABLE hs_header WITH TABLE KEY ebeln = itab-ebeln.

IF sy-subrc = 0.

MOVE-CORRESPONDING itab TO item.

APPEND item TO hs_header-items.

MODIFY TABLE hs_header.

ELSE.

MOVE-CORRESPONDING itab TO hs_header.

MOVE-CORRESPONDING itab TO item.

APPEND item TO hs_header-items.

INSERT table hs_header.

ENDIF.

ENDLOOP.

LOOP AT hs_header.

CLEAR it_out.

it_out-ebeln = hs_header-ebeln.

LOOP AT hs_header-items INTO item.

CONCATENATE it_out-lines ',' item-ebelp INTO it_out-lines.

ENDLOOP.

APPEND it_out.

ENDLOOP.

GET RUN TIME FIELD t2.

t1 = t2 - t1.

WRITE / t1.

最后得出结论：实践出真知，验证之后才知道真正的结果。
流传于ABAP之间的join 不能超过几个表等缪传坑害不少人啊，不能同的情况有不同的优化方案，所以遇到问题时，别急着相信别人的答案，自己先run一下吧。

上面代码出自老白之手，在此声明。

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SAP ABAP的效率问题与代码优化的小思考

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