perl DBI memory leak - perl

Question

I'm having some memory leak issues in a perl script that I'm running for extended periods of time, where the amount of memory that perl is taking up just continues to grow. Because of this, I am trying to use Devel::Leak to track down the leak. I discovered that whenever I call DBI's prepare method, the number of scalar values returned by Devel::Leak goes up by one. Below is I test script I've put together that does what I'm describing:
#!/usr/bin/perl
use strict;
use Devel::Leak;
use DBI;
START:
my $handle; # apparently this doesn't need to be anything at all
my $leaveCount = 0;
my $enterCount = Devel::Leak::NoteSV($handle);
print "ENTER: $enterCount SVs\n";
{
# CONFIG VARIABLES
my $platform = "mysql";
my $database = "db";
my $host = "localhost";
my $port = "3306";
my $user = "user";
my $pw = "pass";
#DATA SOURCE NAME
my $dsn = "dbi:mysql:$database:$host:3306";
# PERL DBI CONNECT
my $dbh = DBI->connect($dsn, $user, $pw);
$dbh->prepare("SELECT * FROM table"); # The script seems to gain one SV without this
# line here, but since this is my issue in my
# main script I decided to leave it in
# undef $dbh; I tried undef-ing this, but it made no difference
}
$leaveCount = Devel::Leak::CheckSV($handle);
print "\nLEAVE: $leaveCount SVs\n";
sleep(1);
goto START;
So is there something I'm doing wrong here, or is this a memory leak in the DBI module? Also, I know that adding one SV every time around the loop isn't a huge deal, and that I most likely have larger memory leaks elsewhere that are causing perl to take so much of the server's memory. However, I'd still like to fix this if I could. Coder's curiosity :)
UPDATE:
The first time through it seems to add about 3,000 SV's, and then every time after that it goes up 1 at a time.

Answer 1

There is a instance of DBI::dr (a blessed hash) living at $DBI::lasth. Check out the ChildHandles key.
#!/usr/bin/perl
use strict;
use warnings;
use Devel::Leak;
use Data::Dumper;
use Symbol::Table;
use DBI;
START:
{
my $handle;
my $enterCount = Devel::Leak::NoteSV($handle);
DB:
{
my $platform = "mysql";
my $database = "db";
my $host = "localhost";
my $port = "3306";
my $user = "user";
my $pw = "pass";
my $dsn = "dbi:mysql:$database:$host:3306";
my $dbh = DBI->connect( $dsn, $user, $pw );
$dbh->prepare("SELECT * FROM table");
$dbh->disconnect();
}
my $st = Symbol::Table->New( 'SCALAR', 'DBI' );
for my $subpkg ( keys %{ $st } ) {
my $val;
{
my $var = "DBI::${subpkg}";
no strict 'refs';
$val = ${$var};
}
print "scalar '$subpkg' => '$val'\n";
}
print Dumper( $DBI::lasth );
$DBI::lasth->{ChildHandles} = []; # <-- reset leaking data structure
my $leaveCount = Devel::Leak::CheckSV($handle);
print "\nCOUNT: $enterCount to $leaveCount SVs\n";
sleep(1);
redo START;
}