ABAP 内表访问表达式的性能

内表访问表达式是ABAP 7.4中引入的重要特性，可以使语句变得更加简洁、美观。那么它的读写性能怎么样呢？我进行了一点点测试。

读取

测试代码，使用三种方式读取同一内表，分别是read table关键字、表达式和read table...binary search：

REPORT ztest_read.


DATA: BEGIN OF gs_test,
        index TYPE i,
        des   TYPE string,
      END OF gs_test.
DATA: gt_test LIKE STANDARD TABLE OF gs_test.


CLASS zcl_reader DEFINITION.

  PUBLIC SECTION.

    METHODS:
      constructor IMPORTING itab LIKE gt_test,
      read_by_read,
      read_by_exp,
      read_by_binary.

  PRIVATE SECTION.

    DATA: lt_test  LIKE STANDARD TABLE OF gs_test.

　　 CLASS-DATA index1 TYPE i VALUE 3769.
　 　CLASS-DATA index2 TYPE i VALUE 5555.

ENDCLASS.


CLASS zcl_reader IMPLEMENTATION.

  METHOD constructor.

    lt_test = itab.
  ENDMETHOD.

  METHOD read_by_read.

    READ TABLE lt_test WITH KEY index = index1 INTO DATA(ls_test).
    READ TABLE lt_test WITH KEY index = index2 INTO ls_test.

  ENDMETHOD.

  METHOD read_by_exp.

    DATA(ls_test) = lt_test[ index = index1 ].
    ls_test = lt_test[ index = index2 ].

  ENDMETHOD.

  METHOD read_by_binary.

    READ TABLE lt_test WITH KEY index = index1 INTO DATA(ls_test) BINARY SEARCH.
    READ TABLE lt_test WITH KEY index = index2 INTO ls_test BINARY SEARCH.

  ENDMETHOD.

ENDCLASS.


INITIALIZATION.

  DATA(des) = '一个字符串'.

  DO 30000 TIMES.

    gs_test-index = gs_test-index + 1.
    gs_test-des   = des.
    APPEND gs_test TO gt_test.

  ENDDO.

  DATA(gr_reader) = NEW zcl_reader( gt_test ).

  gr_reader->read_by_read( ).
  gr_reader->read_by_exp( ).
  gr_reader->read_by_binary( ).

结果：

如图，内表访问表达式在读取方面的性能和read table是一样的。所以，表达式在这里只是read table的简写方式。

修改

测试代码，分别使用modify关键字，内表访问表达式，field symbol来修改内表：

*&---------------------------------------------------------------------*
*& Report  ZTEST_ITAB_MODIFY
*&
*&---------------------------------------------------------------------*
*&
*&
*&---------------------------------------------------------------------*
REPORT ztest_itab_modify.


DATA: BEGIN OF gs_test,
        index TYPE i,
        des   TYPE string,
      END OF gs_test.
DATA: gt_test LIKE STANDARD TABLE OF gs_test.


CLASS zcl_editor DEFINITION.


  PUBLIC SECTION.

    METHODS:
      constructor IMPORTING itab LIKE gt_test,

      modify_by_modify,

      modify_by_exp,

      modify_by_fs.

  PRIVATE SECTION.

    CLASS-DATA new_string TYPE string VALUE '喵喵喵?'.

    DATA: lt_test1  LIKE STANDARD TABLE OF gs_test.
    DATA: lt_test2  LIKE STANDARD TABLE OF gs_test.
    DATA: lt_test3  LIKE STANDARD TABLE OF gs_test.

ENDCLASS.


CLASS zcl_editor IMPLEMENTATION.

  METHOD constructor.

    lt_test1 = itab.
    lt_test2 = itab.
    lt_test3 = itab.

  ENDMETHOD.

  METHOD modify_by_modify.

    DATA idx TYPE i VALUE 1.

    DO lines( lt_test1 ) TIMES.

      READ TABLE lt_test1 INTO DATA(ls_test) INDEX idx .
      ls_test-des =  new_string.
      MODIFY lt_test1 FROM ls_test INDEX idx.
      idx = idx + 1.

    ENDDO.

  ENDMETHOD.

  METHOD modify_by_exp.

    DATA idx TYPE i VALUE 1.

    DO lines( lt_test2 ) TIMES.

      lt_test2[ idx ]-des = new_string.
      idx = idx + 1.

    ENDDO.

  ENDMETHOD.

  METHOD modify_by_fs.

    DATA idx TYPE i VALUE 1.
    FIELD-SYMBOLS: <fs> LIKE gs_test.

    DO lines( lt_test3 ) TIMES.

      READ TABLE lt_test1 ASSIGNING <fs> INDEX idx .
      <fs>-des =  new_string.
      idx = idx + 1.

    ENDDO.

  ENDMETHOD.

ENDCLASS.


INITIALIZATION.

  DATA(des) = '一个字符串'.

  DO 30000 TIMES.

    gs_test-index = gs_test-index + 1.
    gs_test-des   = des.
    APPEND gs_test TO gt_test.

  ENDDO.


  DATA(lr_editor) = NEW zcl_editor( gt_test ).

  lr_editor->modify_by_modify( ).
  lr_editor->modify_by_exp( ).
  lr_editor->modify_by_fs( ).

结果：

可以看出，内表访问表达式在修改普通的标准表时的性能是要稍差于modify关键字的。更不如field symbol。

当然，本文中使用的例子不能代表实际业务场景，因此只可以用作参考。