protected function _configureColumns()
    {
        if (empty($this->columns)) {
            $this->guessColumns();
        }
        $this->_sourceColumns = $this->columns;;

        $columnsByKey = [];
        foreach ($this->columns as $column) {
            $columnKey = $this->_getColumnKey($column);
            for ($j = 0; true; $j++) {
                $suffix = ($j) ? '_' . $j : '';
                $columnKey .= $suffix;
                if (!array_key_exists($columnKey, $columnsByKey)) {
                    break;
                }
            }
            $columnsByKey[$columnKey] = $column;
        }

        $this->columns = $columnsByKey;
    }