search_query_alter.module

<?php

/**
 * @file
 * Test module that alters search queries.
 */

use Drupal\Core\Database\Query\AlterableInterface;

/**
 * Implements hook_query_TAG_alter(): tag search_$type with $type node_search.
 */
function search_query_alter_query_search_node_search_alter(AlterableInterface $query) {
  // For testing purposes, restrict the query to node type 'article' only.
  $query->condition('n.type', 'article');
}