next if !defined $value || $value eq ''; # 0 is fine
if ('HASH' eq ref $value) {
my ($query, $more_objects) = flatten($value, _prefix($prefix, $key));
next if !defined $value || $value eq ''; # 0 is fine
if ('HASH' eq ref $value) {
my ($query, $more_objects) = flatten($value, _prefix($prefix, $key));