$sth->bind_param(1, $folder, SQL_BLOB);
$sth->execute;
my ($fid) = $sth->fetchrow_array;
if (defined $fid) { # for downgrade+upgrade (1.8 -> 1.7 -> 1.8)
$sth->bind_param(1, $folder, SQL_BLOB);
$sth->execute;
my ($fid) = $sth->fetchrow_array;
if (defined $fid) { # for downgrade+upgrade (1.8 -> 1.7 -> 1.8)