class Score

1. 9.x drupal/core/modules/search/lib/Drupal/search/Plugin/views/field/Score.php \Drupal\search\Plugin\views\field\Score
2. 9.x drupal/core/modules/search/lib/Drupal/search/Plugin/views/sort/Score.php \Drupal\search\Plugin\views\sort\Score

class Score extends Numeric {
  protected function defineOptions() {
    $options = parent::defineOptions();
    $options['alternate_sort'] = array(
      'default' => '',
    );
    $options['alternate_order'] = array(
      'default' => 'asc',
    );
    return $options;
  }
  public function buildOptionsForm(&$form, &$form_state) {
    $style_options = $this->view->display_handler
      ->getOption('style_options');
    if (isset($style_options['default']) && $style_options['default'] == $this->options['id']) {
      $handlers = $this->view->display_handler
        ->getHandlers('field');
      $options = array(
        '' => t('No alternate'),
      );
      foreach ($handlers as $id => $handler) {
        $options[$id] = $handler
          ->adminLabel();
      }
      $form['alternate_sort'] = array(
        '#type' => 'select',
        '#title' => t('Alternative sort'),
        '#description' => t('Pick an alternative default table sort field to use when the search score field is unavailable.'),
        '#options' => $options,
        '#default_value' => $this->options['alternate_sort'],
      );
      $form['alternate_order'] = array(
        '#type' => 'select',
        '#title' => t('Alternate sort order'),
        '#options' => array(
          'asc' => t('Ascending'),
          'desc' => t('Descending'),
        ),
        '#default_value' => $this->options['alternate_order'],
      );
    }
    parent::buildOptionsForm($form, $form_state);
  }
  public function query() {

    // Check to see if the search filter added 'score' to the table.
    // Our filter stores it as $handler->search_score -- and we also
    // need to check its relationship to make sure that we're using the same
    // one or obviously this won't work.
    foreach ($this->view->filter as $handler) {
      if (isset($handler->search_score) && $handler->relationship == $this->relationship) {
        $this->field_alias = $handler->search_score;
        $this->tableAlias = $handler->tableAlias;
        return;
      }
    }

    // Hide this field if no search filter is in place.
    $this->options['exclude'] = TRUE;
    if (!empty($this->options['alternate_sort'])) {
      if (isset($this->view->style_plugin->options['default']) && $this->view->style_plugin->options['default'] == $this->options['id']) {

        // Since the style handler initiates fields, we plug these values right into the active handler.
        $this->view->style_plugin->options['default'] = $this->options['alternate_sort'];
        $this->view->style_plugin->options['order'] = $this->options['alternate_order'];
      }
    }
  }
  function render($values) {

    // Only render if we exist.
    if (isset($this->tableAlias)) {
      return parent::render($values);
    }
  }

}