private function getOriginalValues($input, $for_update) {
		// process primary key
		$this->full_pk = false;
		$this->loadPk($input);
		// load values if we have full pk
		if ($this->full_pk) {
			$temp = $this->loadValues($for_update);
			if ($temp !== false) {
				$this->original_values = $temp;
				$this->values_loaded = true;
			}
		}
	}