For a project I am working on migrating UNIX applications to Linux. Most of the scripting work supposed to be done in India, and that is where the issues came in. First you have a developer who knows how to work with M$ Technet and never worked with PERL before (at least 80% of the scripts is written in PERL).
First of all I introduced the user Net::LDAP within PERL, because they first did a ldapsearch, put the output into a ASCII file… and with a PERL script they structured the data… and loaded it into a Oracle database… so that was the first improvement.
Next there were several issues, like not good reading or understanding LDAP/PERL at all…
But at a certain moment, they start complaining about the fact that one of the scripts was slow… on the old system the script had a run time of 4 hours… and now it is up to 28 hours(!!!) 
So they requested me to investigate this.
First I found a ‘main’ kornshell script doing the next thing:
for VAR in a b d e f g i j k m n o p q r s t u v w x y z
do
  for NAME in “‘” a b c d e f g h i j k l m n o p q r s t u v w x y z
  do
    ldap_script.pl $NAME $VAR
  done
done
The content of the ldap_script.pl was something like:
#!/usr/bin/perl
use Net::LDAP;
$ldap = Net::LDAP->new($LDAP_SERVER);
$ldap->bind($LDAP_DN, password=>$LDAP_PASSWD) or die “Cannot connect”;
$LDAP_FILTER=”(&(sn=$ARGV[0]*)(OfficeName=$ARGV[1]*))”;
$mesg = $ldap->search(base=>$LDAP_BASE,
                     filter=>$LDAP_FILTER,
                    ) or die “Cannot connect”;
push(@ENTRIES,$mesg->entries);
$ldap->unbind;
I thought that this costs a lot… loading PERL script, connecting to server, binding to it… et cetera… And this was done in the original script > 2000 times 
So… I removed the loop out of the mainscript… and implemented it into the PERL-script, like this:
#!/usr/bin/perl
use Net::LDAP;
$ldap = Net::LDAP->new($LDAP_SERVER);
@LOOP=(“a”,”b”,”c”,”d”,”e”,”f”,”g”,”h”,”i”,”j”,”k”,”l”,”m”,”n”,”o”,
      “p”,”q”,”r”,”s”,”t”,”u”,”v”,”w”,”x”,”y”,”z”, “‘”);
$ldap->bind($LDAP_DN, password=>$LDAP_PASSWD) or die “Cannot connect”;
foreach $LOOP1 (@LOOP)
{
 foreach $LOOP2 (@LOOP)
 {
    $LDAP_FILTER=”(&(sn=$LOOP1*)(OfficeName=$LOOP2*))”;
    $mesg = $ldap->search(base=>$LDAP_BASE,
                          filter=>$LDAP_FILTER,
                         ) or die “Cannot connect”;
    push(@ENTRIES,$mesg->entries);
 }
}
$ldap->unbind;
And this runs within 3 hours!!! And it is flying! 
There can be done more performance tuning… but that will be another project!
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