Performance issue: CALL FUNCTION inside a Loop.

Question

Hi Friends
I have a Performance Issue. That is, inside a loop...endloop a CALL FUNCTION has been used which gets data from another database table. Finally it's appended into another internal table. Please see this :
  LOOP AT i_mdkp.
    REFRESH lt_mdtbx.
    CLEAR lt_mdtbx.
    CALL FUNCTION 'READ_MRP_LIST'
      EXPORTING
        idtnum        = i_mdkp-dtnum
        icflag        = 'X'
      tables
        mdtbx         = lt_mdtbx
    APPEND LINES OF lt_mdtbx TO i_mdtb.
  ENDLOOP.
It happens for each record available in i_mdkp. Suppose, i_mdkp have around 50000 records, it needs to call the function module till that much time.
So, I want to split it. Can I?
Please give me your valueable suggestions.
Regards
Senthil

Answer 1

If internal table i_mdkp has 50,000 records it does not mean that you need to run 50,000 iterations. You just need dtnum from internal table i_mdkp so you number of iterations should be eqaul to the unique number of dtnum in the internal table. Sort the internal table by dtnum and delete adjacent duplicates from the internal table comparing dtnum before looping. Look at the code below.
DATA i_mdkp_tmp LIKE TABLE OF i_mdkp.
IF NOT i_mdkp[] IS INITIAL.
  i_mdkp_tmp[] = i_mdkp[].
  SORT i_mdkp BY dtnum.
  DELETE ADJACENT DUPLICATES FROM i_mdkp COMPARING dtnum.
  REFRESH i_mdtb.
  LOOP AT i_mdkp.
    CALL FUNCTION 'READ_MRP_LIST'
      EXPORTING
        idtnum = i_mdkp-dtnum
        icflag = 'X'
      TABLES
        mdtbx = lt_mdtbx.
    APPEND LINES OF lt_mdtbx TO i_mdtb.
    REFRESH lt_mdtbx.
  ENDLOOP.
  i_mdkp[] = i_mdkp_tmp[]
ENDIF.