Re: Interesting PL/SQL Puzzle

Yes, you are right, of course. Using large PL/SQL tables and string manipulation (INSTR,SUBSTR and alike) are known to be CPU intensive and there is no way around it. The only way to help an application which uses those functions extensively is to add a column which extracts portion of the original string and populate it with a trigger.

On 11/09/2003 10:59:25 PM, Cary Millsap wrote:
> I agree as Step 1, but I expect that you'll find quickly that the issue
> is a big c value for the EXEC on the block. If you do find this, then it
> indicates exactly what's been suggested several times already: use
> DBMS_PROFILER to dig into the response time of the EXEC.
>
>
> Cary Millsap
> Hotsos Enterprises, Ltd.
> http://www.hotsos.com
>
> Upcoming events:
> - Performance Diagnosis 101: 11/19 Sydney, 12/16 Detroit
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> - Visit www.hotsos.com for schedule details...
>
>
> -----Original Message-----
> Mladen Gogala
> Sent: Saturday, November 08, 2003 2:29 PM
> To: Multiple recipients of list ORACLE-L
>
> Let me give you a carystic advice: run your app with 10046, lev 8 and
> see
> what are you waiting on and how long the waits are.
>
> On 2003.11.08 13:09, "Khedr, Waleed" wrote:
> > I have a weird problem. It seems that execution speed of pl/sql proc
> can
> > slow down dramatically as the size of the proc goes up even if nothing
> gets
> > executed.
> >
> > Let me explain:
> >
> > I have a proc that looks like:
> >
> > Proc test_1 (p1 in out varchar2, p2 in out varchar2) as
> > <some declared variables>
> > begin
> > if condition1 then
> > <big block for string manipulation, two pages of code (substr,
> instr,
> > etc)>
> > end if;
> > if condition2 then
> > <another big block for string manipulation, two pages of code
> (substr,
> > instr, etc)>
> > end if;
> > end;
> >
> >
> > If I change the proc to do nothing by altering it this way:
> >
> > Proc test_2 (p1 in out varchar2, p2 in out varchar2) as
> > <some declared variables>
> > begin
> > if false then
> > <big block for string manipulation>
> > end if;
> > if false then
> > <another big block for string manipulation>
> > end if;
> > end;
> >
> > The execution speed goes up a little bit but is still at least 50
> percent
> > slower than if I change the proc by removing the code in the "if"
> clause,
> > look below:
> >
> > Proc test_3 (p1 in out varchar2, p2 in out varchar2) as
> > <some declared variables>
> > begin
> > if false then
> > null;
> > end if;
> > if false then
> > null;
> > end if;
> > end;
> >
> >
> > proc test_3 ran 30 million times in 9 minutes while test_2 ran in 20
> > minutes.
> > Also test_2 required more CPU resources while running.
> >
> > Also I tried native compilation, which did not do a lot (only 10 %
> faster).
> > When I looked at the C code generated by the native compilation, I was
> not
> > very pleased the way native compilation works.
> >
> >
> > Does anybody have a clue why?
> >
> > I tried to include the proc in a package and pin it but there was no
> > difference.
> >
> >
> > Thanks
> >
> > Waleed
> >
> > --
> > Please see the official ORACLE-L FAQ: http://www.orafaq.net
> > --
> > Author: Khedr, Waleed
> > INET: Waleed.Khedr_at_FMR.COM
> >
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>
> --
> Mladen Gogala
> Oracle DBA
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: Mladen Gogala
> INET: mgogala_at_adelphia.net
>
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> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: Cary Millsap
> INET: cary.millsap_at_hotsos.com
>
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>

Mladen Gogala
Oracle DBA

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-- 
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-- 
Author: Mladen Gogala
  INET: mladen_at_wangtrading.com

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