/**
 * Implements hook_ranking().
 */
function {{ machine_name }}_ranking() {
  // If voting is disabled, we can avoid returning the array, no hard feelings.
  if (\Drupal::config('vote.settings')->get('node_enabled')) {
    return [
      'vote_average' => [
        'title' => t('Average vote'),
        // Note that we use i.sid, the search index's search item id, rather than
        // n.nid.
        'join' => [
          'type' => 'LEFT',
          'table' => 'vote_node_data',
          'alias' => 'vote_node_data',
          'on' => 'vote_node_data.nid = i.sid',
        ],
        // The highest possible score should be 1, and the lowest possible score,
        // always 0, should be 0.
        'score' => 'vote_node_data.average / CAST(%f AS DECIMAL)',
        // Pass in the highest possible voting score as a decimal argument.
        'arguments' => [\Drupal::config('vote.settings')->get('score_max')],
      ],
    ];
  }
}