Score.php

<?php

namespace Drupal\search\Plugin\views\sort;

use Drupal\views\Plugin\views\sort\SortPluginBase;

/**
 * Sort handler for sorting by search score.
 *
 * @ingroup views_sort_handlers
 *
 * @ViewsSort("search_score")
 */
class Score extends SortPluginBase {
    
    /**
     * {@inheritdoc}
     */
    public function query() {
        // Check to see if the search filter/argument added 'score' to the table.
        // Our filter stores it as $handler->search_score -- and we also
        // need to check its relationship to make sure that we're using the same
        // one or obviously this won't work.
        foreach ([
            'filter',
            'argument',
        ] as $type) {
            foreach ($this->view->{$type} as $handler) {
                if (isset($handler->search_score) && $handler->relationship == $this->relationship) {
                    $this->query
                        ->addOrderBy(NULL, NULL, $this->options['order'], $handler->search_score);
                    $this->tableAlias = $handler->tableAlias;
                    return;
                }
            }
        }
        // Do nothing if there is no filter/argument in place. There is no way
        // to sort on scores.
    }

}