sap abap parallel cursor method for nested loop

Parallel Cursor

             Traditionally in abap, the consultant use where clause in nested loop, this is very common but there is big issue with performance when using where clause in nested loop with table, EKKO, VBAK, BKPF etc.

             The problem with this method is for each record in the first internal table, when system checking for the matching record in second table, it search all the records starting from index 1 to the last record.

             To overcome the performance issue , there is a method called parallel cursor, in this method before the loop in second table, first we read the index of the matching record in second table , and then loop get starts from the that index only and exist , when record not match. In this method for each record of first table system check and perform logic only for the match records of second table

      

Traditional Method:

	loop at gt_ekko into gs_ekko.
1	4500000010
2	4500000011
3	4500000012
4	4500000013
5	4500000014
6	4500000015
	loop at gt_ekpo into gs_ekpo where ebeln = gs_ekk-ebeln.
1	4500000010		10
2	4500000010		20
3	4500000011		10
4	4500000011		20
5	4500000012		10
6	4500000013		10
7	4500000014		10
8	4500000015		10
	clear : gs_ekpo.
	endloop.
	clear : gs_ekko.
	endloop.

     Parallel Cursor:

	loop at gt_ekko into gs_ekko.
1	4500000010
2	4500000011
3	4500000012
4	4500000013
5	4500000014
6	4500000015
	Reab table gt_ekpo into gs_ekpo with key ebeln = gs_ekko-ebeln
	if sy-subrc = 0.
	loop at gt_ekpo into gs_ekpo from sy-tabix
	if gs_ekko-ebeln ne gs_ekpo-ebeln.
	exit
	endif.
1	4500000010		10
2	4500000010		20
3	4500000011		10
4	4500000011		20
5	4500000012		10
6	4500000013		10
7	4500000014		10
8	4500000015		10
	clear : gs_ekpo.
	endloop.
	endif.
	clear : gs_ekko.
	endloop.

code using where clause

REPORT ZAFAR_NESTED_LOOP.


data : lv_starttime type TIMESTAMPL,
       lv_endtime type TIMESTAMPL,
       lv_runtime type TIMESTAMPL.



select * from ekko into TABLE @data(gt_ekko) UP TO 10000 ROWS.

if gt_ekko[] is NOT INITIAL.

select * from ekpo into TABLE @data(gt_ekpo) FOR ALL ENTRIES IN @gt_ekko
WHERE EBELN = @GT_EKKO-EBELN.

endif.

SORT GT_EKKO.
SORT GT_EKPO.

GET TIME STAMP FIELD LV_STARTTIME.


LOOP at gt_ekko into data(gs_ekko).

loop at gt_ekpo into data(gs_ekpo) WHERE ebeln = gs_ekko-ebeln.



clear : gs_ekpo.
endloop.

clear : gs_ekko.
endloop.

get TIME STAMP FIELD LV_ENDTIME.

LV_RUNTIME = LV_ENDTIME - LV_STARTTIME.


write : / lv_runtime.
write : / LV_ENDTIME.
write : / LV_STARTTIME.

output in 6.7 seconds

Code using Parallel cursor method :

REPORT ZAFAR_NESTED_LOOP_PC.


data : lv_starttime type TIMESTAMPL,
       lv_endtime type TIMESTAMPL,
       lv_runtime type TIMESTAMPL.


select * from ekko into TABLE @data(gt_ekko) UP TO 10000 ROWS.

if gt_ekko[] is NOT INITIAL.

select * from ekpo into TABLE @data(gt_ekpo) FOR ALL ENTRIES IN @gt_ekko
WHERE EBELN = @GT_EKKO-EBELN.

endif.

SORT GT_EKKO.
SORT GT_EKPO.

GET TIME STAMP FIELD LV_STARTTIME.


LOOP at gt_ekko into data(gs_ekko).

read TABLE gt_ekpo into data(gs_ekpo) with key ebeln = gs_ekko-ebeln BINARY SEARCH.

if sy-subrc = 0.

loop at gt_ekpo into gs_ekpo FROM sy-tabix.

 if gs_ekpo-ebeln ne gs_ekko-ebeln.
    exit.
 endif.


clear : gs_ekpo.
endloop.

endif.

clear : gs_ekko.
endloop.

get TIME STAMP FIELD LV_ENDTIME.

LV_RUNTIME = LV_ENDTIME - LV_STARTTIME.


write : / lv_runtime.
write : / LV_ENDTIME.
write : / LV_STARTTIME.

Same records using parallel cursor method output in 0.0089 seconds.