SAP ABAP程序性能优化

来源：互联网发布：兼职淘宝摄影师招聘编辑：程序博客网时间：2024/04/28 04:18

For all entries

The for all entries creates a where clause, where all the entries in the driver table are combined with OR. If the number of entries in the driver table is larger than rsdb/max_blocking_factor, several similar SQL statements are executed to limit the length of the WHERE clause.

The plus

Large amount of data
Mixing processing and reading of data
Fast internal reprocessing of data
Fast

The Minus

Difficult to program/understand
Memory could be critical (use FREE or PACKAGE size)

Some steps that might make FOR ALL ENTRIES more efficient:

Removing duplicates from the driver table
Sorting the driver table

If possible, convert the data in the driver table to ranges so a BETWEEN statement is used instead of and OR statement:

               FOR ALL ENTRIES IN i_tab

                  WHERE mykey >= i_tab-low and             mykey <= i_tab-high.

Nested selects

The plus:

Small amount of data
Mixing processing and reading of data
Easy to code - and understand

The minus:

Large amount of data
when mixed processing isn’t needed
Performance killer no. 1

Select using JOINS

The plus

Very large amount of data
Similar to Nested selects - when the accesses are planned by the programmer
In some cases the fastest
Not so memory critical

The minus

Very difficult to program/understand
Mixing processing and reading of data not possible

Use the selection criteria

SELECT * FROM SBOOK.

  CHECK: SBOOK-CARRID = 'LH' AND

                  SBOOK-CONNID = '0400'.

ENDSELECT.

SELECT * FROM SBOOK

  WHERE CARRID = 'LH' AND

        CONNID = '0400'.

ENDSELECT.

Use the aggregated functions

C4A = '000'.

SELECT * FROM T100

  WHERE SPRSL = 'D' AND

        ARBGB = '00'.

  CHECK: T100-MSGNR > C4A.

  C4A = T100-MSGNR.

ENDSELECT.

SELECT MAX( MSGNR ) FROM T100 INTO C4A

 WHERE SPRSL = 'D' AND

       ARBGB = '00'.

Select with view

SELECT * FROM DD01L

  WHERE DOMNAME LIKE 'CHAR%'

        AND AS4LOCAL = 'A'.

  SELECT SINGLE * FROM DD01T

    WHERE   DOMNAME    = DD01L-DOMNAME

        AND AS4LOCAL   = 'A'

        AND AS4VERS    = DD01L-AS4VERS

        AND DDLANGUAGE = SY-LANGU.

ENDSELECT.

SELECT * FROM DD01V

 WHERE DOMNAME LIKE 'CHAR%'

       AND DDLANGUAGE = SY-LANGU.

ENDSELECT.

Select with index support

SELECT * FROM T100

 WHERE     ARBGB = '00'

       AND MSGNR = '999'.

ENDSELECT.

SELECT * FROM T002.

  SELECT * FROM T100

    WHERE     SPRSL = T002-SPRAS

          AND ARBGB = '00'

          AND MSGNR = '999'.

  ENDSELECT.

ENDSELECT.

Select … Into table

REFRESH X006.

SELECT * FROM T006 INTO X006.

  APPEND X006.

ENDSELECT

SELECT * FROM T006 INTO TABLE X006.

Select with selection list

SELECT * FROM DD01L

  WHERE DOMNAME LIKE 'CHAR%'

        AND AS4LOCAL = 'A'.

ENDSELECT

SELECT DOMNAME FROM DD01L

 INTO DD01L-DOMNAME

 WHERE DOMNAME LIKE 'CHAR%'

       AND AS4LOCAL = 'A'.

ENDSELECT

Key access to multiple lines

LOOP AT TAB.

 CHECK TAB-K = KVAL.

 " ...

ENDLOOP.

LOOP AT TAB WHERE K = KVAL.

  " ...

ENDLOOP.

Copying internal tables

REFRESH TAB_DEST.

LOOP AT TAB_SRC INTO TAB_DEST.

  APPEND TAB_DEST.

ENDLOOP.

TAB_DEST[] = TAB_SRC[].

Modifying a set of lines

LOOP AT TAB.

  IF TAB-FLAG IS INITIAL.

    TAB-FLAG = 'X'.

  ENDIF.

  MODIFY TAB.

ENDLOOP.

TAB-FLAG = 'X'.

MODIFY TAB TRANSPORTING FLAG

           WHERE FLAG IS INITIAL.

Deleting a sequence of lines

DO 101 TIMES.

  DELETE TAB_DEST INDEX 450.

ENDDO.

DELETE TAB_DEST FROM 450 TO 550.

Linear search vs. binary

READ TABLE TAB WITH KEY K = 'X'.

READ TABLE TAB WITH KEY K = 'X' BINARY SEARCH.

Comparison of internal tables

DESCRIBE TABLE: TAB1 LINES L1,

                TAB2 LINES L2.

IF L1 <> L2.

  TAB_DIFFERENT = 'X'.

ELSE.

  TAB_DIFFERENT = SPACE.

  LOOP AT TAB1.

    READ TABLE TAB2 INDEX SY-TABIX.

    IF TAB1 <> TAB2.

      TAB_DIFFERENT = 'X'. EXIT.

    ENDIF.

  ENDLOOP.

ENDIF.

IF TAB_DIFFERENT = SPACE.

  " ...

ENDIF.

IF TAB1[] = TAB2[].

 " ...

ENDIF.

Modify selected components

LOOP AT TAB.

 TAB-DATE = SY-DATUM.

 MODIFY TAB.

ENDLOOP.

WA-DATE = SY-DATUM.

LOOP AT TAB.

 MODIFY TAB FROM WA TRANSPORTING DATE.

ENDLOOP.

Appending two internal tables

LOOP AT TAB_SRC.

  APPEND TAB_SRC TO TAB_DEST.

ENDLOOP

APPEND LINES OF TAB_SRC TO TAB_DEST.

Deleting a set of lines

LOOP AT TAB_DEST WHERE K = KVAL.

  DELETE TAB_DEST.

ENDLOOP

DELETE TAB_DEST WHERE K = KVAL.

Tools available in SAP to pin-point a performance problem

·                The runtime analysis (SE30)

·                SQL Trace (ST05)

·                Tips and Tricks tool

·                The performance database

Optimizing the load of the database

Using table buffering

Using buffered tables improves the performance considerably. Note that in some cases a statement can not be used with a buffered table, so when using these statements the buffer will be bypassed. These statements are:

Select DISTINCT
ORDER BY / GROUP BY / HAVING clause
Any WHERE clause that contains a sub query or IS NULL expression
JOIN s
A SELECT... FOR UPDATE

If you wan t to explicitly bypass the buffer, use the BYPASS BUFFER addition to the SELECT clause.

Use the ABAP SORT Clause Instead of ORDER BY

The ORDER BY clause is executed on the database server while the ABAP SORT statement is executed on the application server. The database server will usually be the bottleneck, so sometimes it is better to move the sort from the database server to the application server.

If you are not sorting by the primary key ( E.g. using the ORDER BY PRIMARY key statement) but are sorting by another key, it could be better to use the ABAP SORT statement to sort the data in an internal table. Note however that for very large result sets it might not be a feasible solution and you would want to let the database server sort it.

Avoid the SELECT DISTINCT Statement

As with the ORDER BY clause it could be better to avoid using SELECT DISTINCT, if some of the fields are not part of an index. Instead use ABAP SORT + DELETE ADJACENT DUPLICATES on an internal table, to delete duplicate rows.

原文地址 http://blog.csdn.net/opparts/archive/2005/02/02/278178.aspx