Magento – Updating ui_bookmark Table When Adding Columns via ui_component XML

In Magento 2 this is handled by the \Magento\Framework\Config\Reader\Filesystem class. This class allows you specify the xml file you want to merge.

The following part will merge all files found in the available modules and merge the output (snippet from \Magento\Framework\Config\Reader\Filesystem)

/**
 * Load configuration scope
 *
 * @param string|null $scope
 * @return array
 */
public function read($scope = null)
{
    $scope = $scope ?: $this->_defaultScope;
    $fileList = $this->_fileResolver->get($this->_fileName, $scope);
    if (!count($fileList)) {
        return [];
    }
    $output = $this->_readFiles($fileList);

    return $output;
}

/**
 * Read configuration files
 *
 * @param array $fileList
 * @return array
 * @throws \Magento\Framework\Exception
 */
protected function _readFiles($fileList)
{
    /** @var \Magento\Framework\Config\Dom $configMerger */
    $configMerger = null;
    foreach ($fileList as $key => $content) {
        try {
            if (!$configMerger) {
                $configMerger = $this->_createConfigMerger($this->_domDocumentClass, $content);
            } else {
                $configMerger->merge($content);
            }
        } catch (\Magento\Framework\Config\Dom\ValidationException $e) {
            throw new \Magento\Framework\Exception("Invalid XML in file " . $key . ":\n" . $e->getMessage());
        }
    }
    if ($this->_isValidated) {
        $errors = [];
        if ($configMerger && !$configMerger->validate($this->_schemaFile, $errors)) {
            $message = "Invalid Document \n";
            throw new \Magento\Framework\Exception($message . implode("\n", $errors));
        }
    }

    $output = [];
    if ($configMerger) {
        $output = $this->_converter->convert($configMerger->getDom());
    }
    return $output;
}

In the solution I created the class above is extended to supply the xml file needed and specify where the xsd file to validate can be found (see https://github.com/Genmato/MageStackTable for complete example):

namespace Genmato\TableXml\Model\Table;

class Reader extends \Magento\Framework\Config\Reader\Filesystem
{
    protected $_idAttributes = [
        '/table/row' => 'id',
        '/table/row/column' => 'id',
    ];

    /**
     * @param \Magento\Framework\Config\FileResolverInterface $fileResolver
     * @param \Magento\Framework\Config\ConverterInterface $converter
     * @param \Genmato\TableXml\Model\Table\SchemaLocator $schemaLocator
     * @param \Magento\Framework\Config\ValidationStateInterface $validationState
     * @param string $fileName
     * @param array $idAttributes
     * @param string $domDocumentClass
     * @param string $defaultScope
     */
    public function __construct(
        \Magento\Framework\Config\FileResolverInterface $fileResolver,
        \Magento\Framework\Config\ConverterInterface $converter,
        \Genmato\TableXml\Model\Table\SchemaLocator $schemaLocator,
        \Magento\Framework\Config\ValidationStateInterface $validationState,
        $fileName = 'table.xml',
        $idAttributes = [],
        $domDocumentClass = 'Magento\Framework\Config\Dom',
        $defaultScope = 'global'
    ) {
        parent::__construct(
            $fileResolver,
            $converter,
            $schemaLocator,
            $validationState,
            $fileName,
            $idAttributes,
            $domDocumentClass,
            $defaultScope
        );
    }

To get the merged data you can then call:

$output = $this->_objectManager->get('Genmato\TableXml\Model\Table\Reader')->read();

The output is then an array representation of the merged xml.

EDIT:

To test the way the files are read I created a working example (see https://github.com/Genmato/MageStackTable). Updated the answer with the solution build.

You could get the data collection being used by the sales order grid, extract the field data, and create an option for each unique result:

class CcTypes implements OptionSourceInterface
{

    /**
     * @var \Magento\Sales\Model\ResourceModel\Order\Grid\Collection
     */
    protected $salesCollection;

    protected $options;

    public function __construct(
        \Magento\Framework\View\Element\UiComponent\DataProvider\CollectionFactory $collectionFactory
    ) {
        $this->salesCollection = $collectionFactory->getReport("sales_order_grid_data_source");
    }

    public function toOptionArray()
    {
        if ($this->options === null) {

            foreach ($this->salesCollection->addOrder('cc_type')->addFieldToSelect('cc_type')->distinct(true) as $order) {
                $ccType = $order->getCcType();
                $this->options[] = [
                    'value' => $ccType,
                    'label' => $ccType
                ];
            }
        }

        return $this->options;
    }
}