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SAP ABAP程序性能优化 2-sql语法

原创 Linux操作系统 作者:chouer523 时间:2019-06-01 13:48:04 0 删除 编辑

作者tag:sap abap CSDN 转:njchouer@hotmail.com


Performance Tuning

Contributed by Henrik Frank

  1. For all entries

  2. Nested selects

  3. Select using JOINS

  4. Use the selection criteria

  5. Use the aggregated functions

  6. Select with view

  7. Select with index support

  8. Select … Into table

  9. Select with selection list

  10. Key access to multiple lines

  11. Copying internal tables

  12. Modifying a set of lines

  13. Deleting a sequence of lines

  14. Linear search vs. binary

  15. Comparison of internal tables

  16. Modify selected components

  17. Appending two internal tables

  18. Deleting a set of lines

  19. Tools available in SAP to pin-point a performance problem

  20. Optimizing the load of the database

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

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