Delete in loop

Question

Hi,
I have a delete statement inside a loop like
LOOP AT DATA_PACKAGE.
    lv_tabix = sy-tabix.
    clear gt_mattab.
    READ TABLE gt_mattab
    WITH KEY MATERIAL = DATA_PACKAGE-MATERIAL.
    IF SY-SUBRC NE 0.
      DELETE DATA_PACKAGE index lv_tabix.
    ENDIF.
  ENLOOP.
Can you please help me in deleting the data packages with out using it in the loop?
Will that increase the performance of the code and how?

Answer 1

Hi Prasad,
Let me explain exactly what happens if u delete a record from the internal table.
If u defined your internal table like TYPE STANDARD TABLE OF or TYPE SORTED TABLE OF then it will work on INDEX mechanism.
So if have 100 records in ur internal table then each record will be identified with its position i.e INDEX. When u delete a record from the table then it has to recreate the indexes for all other records(Except in case of deletion of last record) after that record. It is the majar disadvantage of delete statement. If u use delete statement inside loop this process has to happen equal to number of deletions.
So there is one more solution for this which will be faster than
DELETE inside the loop. Instead of deleting the records from the original table APPEND the records to another internal table.In this case it has to create INDEX for one time for one append in contrary to DELETE whcih has to recreate INDEXS for all rows.
Check the logic below. Implement and use SQL trace to moniter the performance(transaction ST05).
LOOP AT DATA_PACKAGE.
lv_tabix = sy-tabix.
clear gt_mattab.
READ TABLE gt_mattab
WITH KEY MATERIAL = DATA_PACKAGE-MATERIAL.
CHECK SY-SUBRC EQ 0.
APPEND DATA_PACKAGE TO DATA_PACKAGE1.
ENLOOP.
Also if u dont have else part and no code after ENDIF then always use CHECK statement which is much faster than IF.
Thanks,
Vinod.
Edited by: Vinod Kumar Vemuru on Mar 20, 2008 6:32 PM