Interesting PL/SQL Puzzle

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

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Author: Khedr, Waleed
  INET: Waleed.Khedr_at_FMR.COM

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