public function addSortOrderMissingFields(SchemaSetupInterface $setup)
    {
        $connection = $setup->getConnection();
        $table      = $setup->getTable('catalog_eav_attribute');

        // Append a column 'sort_order_asc_missing' into the db.
        $connection->addColumn(
            $table,
            'sort_order_asc_missing',
            [
                'type'     => \Magento\Framework\DB\Ddl\Table::TYPE_TEXT,
                'nullable' => false,
                'default'  => \Smile\ElasticsuiteCore\Search\Request\SortOrderInterface::MISSING_LAST,
                'length'   => 10,
                'comment'  => 'Sort products without value when sorting ASC',
            ]
        );

        // Append a column 'sort_order_desc_missing' into the db.
        $connection->addColumn(
            $table,
            'sort_order_desc_missing',
            [
                'type'     => \Magento\Framework\DB\Ddl\Table::TYPE_TEXT,
                'nullable' => false,
                'default'  => \Smile\ElasticsuiteCore\Search\Request\SortOrderInterface::MISSING_FIRST,
                'length'   => 10,
                'comment'  => 'Sort products without value when sorting DESC',
            ]
        );
    }