problem with subclassing DBI and " is not a DBI handle (has no magic)" error

[Martin J. Evans]

Hi,

This is a fairly complex setup to explain so I'll initially try and keep 
it simple and can expand it necessary. I'm getting the error

$ perl a.pl
SV = RV(0x9fa6df4) at 0xa4450e8
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0xa4451a8
dbih_getcom handle HASH(0xa4451a8) is not a DBI handle (has no magic) at 
/usr/lib/perl5/site_perl/5.8.8/DBIx/Log4perl/db.pm line 61.

I'm using DBI 1.51 and DBD::Oracle 1.17 and DBIx::Log4perl 0.05.
DBIx::log4perl is overriding most methods in DBI.

I'm running a script like this:

use XXX::DB;
use Log::Log4perl qw(get_logger :levels);
Log::Log4perl->init_and_watch("/etc/log4.conf", 60);
my $zzz = XXX::DB->new(
{DSN =>"dbi:Oracle:XE",User=>"xxx", Pass=>"yyy"});
my $dbh = $zzz->connect() or die "$DBD::errstr";
$dbh->selectrow_array("select x_entry_status_id from v_market_entries 
where entry_id = ? and market_id = ?", undef, 31, 11);

where XXX:DB just provides some extra methods not in DBI to
avoid differences in DBD::oracle, DBD::DB2 and DBD::mysql and
uses Log::Log4perl::get_logger but it only comes in to this in that it 
uses DBIx::Log4perl.

If the script is changed to omit the DBIx::Log4perl it becomes:

use DBI;
my $dbh = DBI->connect("dbi:Oracle:XE", "xxx", "yyy",{RaiseError => 1}) 
or die "$DBD::errstr";
$dbh->selectrow_array("select entry_status_id from v_market_entries 
where x_entry_id = ? and market_id = ?", undef, 31, 11);

The first thing to note is the second script works.
The second thing to note is that the column x_entry_id does NOT exist.
If the selectrow_array SQL is for a column that does exist it
works fine in both scripts.

I've read:

+One more thing to note: you must let the DBI do the handle creation.
+If you want to override the connect() method in your *::dr class then
+it must still call SUPER::connect to get a $dbh to work with.
+Similarly, an overridden prepare() method in *::db must still call
+SUPER::prepare to get a $sth. If you try to create your own handles
+using bless() then you'll find the DBI will reject them with an "is not
+a DBI handle (has no magic)" error.

from the DBI changelog and it would suggest I've done something wrong
when overriding the methods in DBI. However, I believe I've done the 
SUPER::connect and SUPER::selectrow_array correctly like this (this
example does omit some extra stuff on the private hash):

sub connect {
    my ($drh, $dsn, $user, $pass, $attr) = @_;
    my %h = ();
    my $dbh = $drh->SUPER::connect($dsn, $user, $pass, $attr);
    return $dbh if (!$dbh);
    # stuff setting $h{xxx}
    $dbh->{private_DBIx_Log4perl} = \%h;
    return $dbh;
}
sub selectrow_array {
    my ($dbh, @args) = @_;

    my $h = $dbh->{private_DBIx_Log4perl};

    if (wantarray) {
        my @ret = $dbh->SUPER::selectrow_array(@args);
        return @ret;

    } else {
        my $ret = $dbh->SUPER::selectrow_array(@args);
        return $ret;
    }
}

The comment in the DBI changelog suggests I've done something wrong.
Any ideas? If more info is required I can provide but I didn't want
to make this too convoluted initially.

Thanks.

Martin