RE: Condition Compilation Question

Conditional compilation eliminates sections from the compiled code
entirely. If you flipped the debug_flag to TRUE, you 'd still be
printing Debug=F until you recompiled your source code. 

 

 

 

________________________________

From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Ethan Post
Sent: Tuesday, May 15, 2007 11:33 AM
To: oracle-l
Subject: Condition Compilation Question

 

I am reading the section regarding conditional compilation here.

http://www.oracle.com/technology/pub/articles/10gdba/nanda_10gr2dba_part
1.html#compile 

What is the difference for the example below and using a standard "if
then else"? Why would below  be better? Isn't it evaluated every time?

------------------------------------------------------------------------
------------------------------------------------------------ 

Let's examine another variation of this new feature. In addition to the
definition of a conditional variable, you can also check a static
constant of a package in the conditional compilation. For example,
suppose you want to control the debugging output of a PL/SQL procedure
based on a Boolean packaged constant. First you create the package as 

create or replace package debug_pkg

is

   debug_flag constant boolean := FALSE;

end;

The debug_flag is the constant that determines the conditional logic in
the code. You can now embed the code inside the package as follows: 

create or replace procedure myproc

as

begin

        $if debug_pkg.debug_flag $then 

                dbms_output.put_line ('Debug=T');

        $else

                dbms_output.put_line ('Debug=F');


        $end

end;

Note that the packaged constant is referenced directly without any $
sign. In this case, there is no need to set any session- or system-level
conditional compilation parameters. While the function is compiled, you
do not need to pass any additional clause either. To see how this works,
execute: 

SQL> exec myproc



Debug=F

Because the value of debug_pkg.debug_flag is FALSE now, the execution of
the procedure returned "F" as expected. Now, change the constant value: 

create or replace package debug_pkg


is

   debug_flag constant boolean := TRUE;

end;

Then, execute the procedure again: 

SQL> exec myproc



Debug=T

The procedure picked up the value of the constant to show "T," as
expected. Note a very important difference here-you did not need to
recompile the procedure; the change to the constant was picked up
automatically!

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