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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，内表访问表达式在修改方面的性能和read是一样的。
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。
ABAP 内表访问表达式的性能
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