+sub _get_primary_key_column {
+ my ($caller_package) = @_;
+ my $meta = $caller_package->meta;
+
+ my $column_name;
+ $column_name = $meta->{primary_key}->{columns}->[0] if $meta->{primary_key} && (ref($meta->{primary_key}->{columns}) eq 'ARRAY') && (1 == scalar(@{ $meta->{primary_key}->{columns} }));
+
+ croak "Unable to retrieve primary key column name: meta information for package $caller_package not set up correctly" unless $column_name;
+
+ return $column_name;
+}