protected function getTableColumns()
    {
        if (0 === count(self::$tableColumns)) {
            $table = $this->getTable();
            $connect = $this->getConnection();
            $builder = $connect->getSchemaBuilder();
            $columns = $builder->getColumnListing($table);

            self::$tableColumns = (array)$columns;
        }
        return self::$tableColumns;
    }