ABAP Enter

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
  
  

   

  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.