class QueryFactory

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

core.services.yml in drupal/core/core.services.yml

drupal/core/core.services.yml

entity.query.config in drupal/core/core.services.yml

Drupal\Core\Config\Entity\Query\QueryFactory

class QueryFactory {

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

  /**
   * Constructs a QueryFactory object.
   *
   * @param \Drupal\Core\Config\StorageInterface $config_storage
   *   The config storage used by the config entity query.
   */
  public function __construct(StorageInterface $config_storage) {
    return $this->configStorage = $config_storage;
  }

  /**
   * Instantiates an entity query for a given entity type.
   *
   * @param string $entity_type
   *   The entity type for the query.
   * @param string $conjunction
   *   The operator to use to combine conditions: 'AND' or 'OR'.
   * @param \Drupal\Core\Entity\EntityManager $entity_manager
   *   The entity manager that handles the entity type.
   *
   * @return \Drupal\Core\Config\Entity\Query\Query
   *   An entity query for a specific configuration entity type.
   */
  public function get($entity_type, $conjunction, EntityManager $entity_manager) {
    return new Query($entity_type, $conjunction, $entity_manager, $this->configStorage);
  }

  /**
   * Returns a aggregation query object for a given entity type.
   *
   * @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 $entity_manager
   *  The entity manager.
   *
   * @throws \Drupal\Core\Entity\Query\QueryException
   * @return \Drupal\Core\Entity\Query\QueryAggregateInterface
   *   The query object that can query the given entity type.
   */
  public function getAggregate($entity_type, $conjunction, EntityManager $entity_manager) {
    throw new QueryException('Aggregation over configuration entities is not supported');
  }

}