class Query

1. 8.x drupal/core/lib/Drupal/Core/Database/Query/Query.php \Drupal\Core\Database\Query\Query
2. 8.x drupal/core/lib/Drupal/Core/Config/Entity/Query/Query.php \Drupal\Core\Config\Entity\Query\Query
3. 8.x drupal/core/modules/field_sql_storage/lib/Drupal/field_sql_storage/Entity/Query.php \Drupal\field_sql_storage\Entity\Query

QueryTest::getInfo in drupal/core/modules/views/lib/Drupal/views/Tests/Plugin/QueryTest.php

views.data_types.schema.yml in drupal/core/modules/views/config/schema/views.data_types.schema.yml

drupal/core/modules/views/config/schema/views.data_types.schema.yml

ViewUI::renderPreview in drupal/core/modules/views_ui/lib/Drupal/views_ui/ViewUI.php

_drupal_decode_exception in drupal/core/includes/errors.inc

Decodes an exception and retrieves the correct caller.

class Query extends QueryBase implements QueryInterface {

  /**
   * Stores the entity manager.
   *
   * @var \Drupal\Core\Entity\EntityManager
   */
  protected $entityManager;

  /**
   * The config storage used by the config entity query.
   *
   * @var \Drupal\Core\Config\StorageInterface
   */
  protected $configStorage;

  /**
   * Constructs a Query object.
   *
   * @param string $entity_type
   *   The entity type.
   * @param string $conjunction
   *   - AND: all of the conditions on the query need to match.
   *   - OR: at least one of the conditions on the query need to match.
   * @param \Drupal\Core\Entity\EntityManager $entity_manager
   *   The entity manager that stores all meta information.
   * @param \Drupal\Core\Config\StorageInterface $config_storage
   *   The actual config storage which is used to list all config items.
   */
  function __construct($entity_type, $conjunction, EntityManager $entity_manager, StorageInterface $config_storage) {
    parent::__construct($entity_type, $conjunction);
    $this->entityManager = $entity_manager;
    $this->configStorage = $config_storage;
  }

  /**
   * Implements \Drupal\Core\Entity\Query\QueryInterface::conditionGroupFactory().
   */
  public function conditionGroupFactory($conjunction = 'AND') {
    return new Condition($conjunction);
  }

  /**
   * Overrides \Drupal\Core\Entity\Query\QueryBase::condition().
   *
   * Additional to the syntax defined in the QueryInterface you can use
   * placeholders (*) to match all keys of an subarray. Let's take the follow
   * yaml file as example:
   * @code
   *  level1:
   *    level2a:
   *      level3: 1
   *    level2b:
   *      level3: 2
   * @endcode
   * Then you can filter out via $query->condition('level1.*.level3', 1).
   */
  public function condition($property, $value = NULL, $operator = NULL, $langcode = NULL) {
    return parent::condition($property, $value, $operator, $langcode);
  }

  /**
   * Implements \Drupal\Core\Entity\Query\QueryInterface::execute().
   */
  public function execute() {

    // Load all config files.
    $entity_info = $this->entityManager
      ->getDefinition($this
      ->getEntityType());
    $prefix = $entity_info['config_prefix'];
    $prefix_length = strlen($prefix) + 1;
    $names = $this->configStorage
      ->listAll($prefix);
    $configs = array();
    foreach ($names as $name) {
      $configs[substr($name, $prefix_length)] = config($name)
        ->get();
    }
    $result = $this->condition
      ->compile($configs);

    // Apply sort settings.
    foreach ($this->sort as $sort) {
      $direction = $sort['direction'] == 'ASC' ? -1 : 1;
      $field = $sort['field'];
      uasort($result, function ($a, $b) use ($field, $direction) {
        return $a[$field] <= $b[$field] ? $direction : -$direction;
      });
    }

    // Let the pager do its work.
    $this
      ->initializePager();
    if ($this->range) {
      $result = array_slice($result, $this->range['start'], $this->range['length'], TRUE);
    }
    if ($this->count) {
      return count($result);
    }

    // Create the expected structure of entity_id => entity_id. Config
    // entities have string entity IDs.
    foreach ($result as $key => &$value) {
      $value = (string) $key;
    }
    return $result;
  }

}