I used the approach provided here to reverse comments order in Drupal 8:

    /** Implements hook_query_TAG_alter().
 * Alter comments query to order by DESC as well as the default ASC.
function MYMODULENAME_query_comment_filter_alter(QueryAlterableInterface $query) {
  $orderby = &$query->getOrderBy();

  // Sorting for threaded comments.
  if (isset($orderby['torder'])) {
    // Sort by root parent first, then normal threaded.
    $query->addExpression("SUBSTRING_INDEX(c.thread, '.', 1)", 'rparent');
    $orderby = array('rparent' => 'DESC') + $orderby;
  // Sorting for flat comments.
  else if (isset($orderby['c.cid'])) {
    $direction = 'DESC';

    $orderby['c.cid'] = $direction;
    $orderby = array('c.created' => $direction) + $orderby;

but I receive the followig error when run the module:

Recoverable fatal error: Argument 1 passed to mymd_query_comment_filter_alter() must be an instance of QueryAlterableInterface, instance of Drupal\Core\Database\Query\PagerSelectExtender given, called in D:\wamp95\www\drupal83\core\lib\Drupal\Core\Extension\ModuleHandler.php on line 501 and defined in mymd_query_comment_filter_alter()

what is the problem and how should I solve it?

  • I think I should use: Drupal\Core\Database\Query\AlterableInterface $query as argument.
    – Mdeh
    Mar 14, 2017 at 14:35

1 Answer 1


I used Drupal\Core\Database\Query\AlterableInterface $query as argument.

It solved the problem.

  • Yes see the docs. It should be AlterableInterface. api.drupal.org/api/drupal/…
    – Kevin
    Mar 14, 2017 at 14:43
  • Yes, you need to use "AlterableInterface" instead of "QueryAlterableInterface". use Drupal\Core\Database\Query\AlterableInterface; function MYMODULENAME_query_comment_filter_alter(AlterableInterface$query) { //..... } May 31, 2021 at 13:06

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