topic Re: Nested LOOPs - Do you recommend? in Application Development and Automation Discussions

Nested LOOPs - Do you recommend?

Former Member — Wed, 19 Dec 2007 10:01:05 GMT

Hi,

I am using a nested LOOP in my print program that uses a form in SAPScript. Please see the code fragment:

LOOP AT it_final INTO wa_final.

LOOP AT it_mseg INTO wa_mseg.

CALL FUNCTION 'WRITE_FORM'

EXPORTING

element = 'HEAD'

type = 'TOP'

window = 'MAIN'.

CALL FUNCTION 'WRITE_FORM'

EXPORTING

element = 'INFO'

type = 'BODY'

window = 'MAIN'.

ENDLOOP.

The internal table IT_MSEG usually contains only minimal number of lines, say less than 10. I can't find an alternative in this particular scenario. Is it gonna make the system considerably slower?

Re: Nested LOOPs - Do you recommend?

Former Member — Wed, 19 Dec 2007 10:08:53 GMT

Hi,

try to use where condition for your second loop base on the values from 1st internal table, may be you have 10 rec in development when coming to production system there may be a chance of getting more records.

Reward if useful.

Thanks,

Sreeram.

Re: Nested LOOPs - Do you recommend?

Former Member — Wed, 19 Dec 2007 10:10:13 GMT

Instead of using nested Select loops it is often better to use subqueries

Check the following link:

how to avoid nested loops in this program to improve the performence

Reward points if useful.

Re: Nested LOOPs - Do you recommend?

Former Member — Wed, 19 Dec 2007 10:26:48 GMT

Hi Arun,

IF it_final is your header level and it_mseg is your item level then I dont think you can avoid this nested loop.

But if you have to select a single entry from it_mseg, then you can do like this,

LOOP AT it_final INTO wa_final.

READ TABLE it_mseg INTO wa_mseg.

CALL FUNCTION 'WRITE_FORM'

EXPORTING

element = 'HEAD'

type = 'TOP'

window = 'MAIN'.

CALL FUNCTION 'WRITE_FORM'

EXPORTING

element = 'INFO'

type = 'BODY'

window = 'MAIN'.

ENDLOOP.

Regards

Sourabh Verma

Re: Nested LOOPs - Do you recommend?

Former Member — Wed, 19 Dec 2007 11:07:22 GMT

Thats the problem Sourabh, It is not a single entry that i take from IT_MSEG. IT_FINAL is at header level. IT_MSEG has line items.

Re: Nested LOOPs - Do you recommend?

Former Member — Wed, 19 Dec 2007 11:14:28 GMT

Dear Sreeram,

Data in IT_MSEG is already filtered based on input in select-options. The problem with your suggestion is, there is no direct link between IT_FINAL and IT_MSEG.

Arun.

Re: Nested LOOPs - Do you recommend?

Former Member — Wed, 19 Dec 2007 11:15:32 GMT

Sravan,

I'm not talking about nested selects. I'm using nested "LOOP AT". In the loop, I'm not touching the database at all.

Re: Nested LOOPs - Do you recommend?

rodrigo_paisante3 — Wed, 19 Dec 2007 11:19:14 GMT

Hi, see this link:

/people/rob.burbank/blog/2006/02/07/performance-of-nested-loops

Rob recomends the indexed or parallel loop...

Regards

Re: Nested LOOPs - Do you recommend?

Former Member — Thu, 20 Dec 2007 04:39:01 GMT

For nested loops problem, go for parellel cursor technique , an eg. simmilar to ur req. header and line item can be printed/processed in the manner as given below.

SORT : it_mara BY matnr ,

it_makt BY matnr .

i = 1.

LOOP AT it_mara INTO wa_mara.

LOOP AT it_makt INTO wa_makt FROM i.

IF wa_makt-matnr <> wa_mara-matnr.

i = sy-tabix.

EXIT.

ENDIF.

write 😕 wa_mara-matnr , wa_makt-MAKTX .

ENDLOOP.

PS: Reward Poins if Helpfull.

Regards

Naveen Gupta

Re: Nested LOOPs - Do you recommend?

Former Member — Thu, 20 Dec 2007 04:46:19 GMT

Thanks for that Naveen. It helped.

Re: Nested LOOPs - Do you recommend?

Former Member — Thu, 20 Dec 2007 04:47:35 GMT

Dear Rodrigo,

That blog by Rob was really worth. Thanks. Thanks to all.

Regards

Arun.