code: public function count($q = '*', $db = null)
      {
          if ($this->emulateExecution) {
              return 0;
          }
  
          if ($this->where === null) {
              /* @var $modelClass ActiveRecord */
              $modelClass = $this->modelClass;
              if ($db === null) {
                  $db = $modelClass::getDb();
              }
  
              return $db->executeCommand('LLEN', [$modelClass::keyPrefix()]);
          } else {
              return $this->executeScript($db, 'Count');
          }
      }
docs: Returns the number of records.
  @param string $q the COUNT expression. This parameter is ignored by this implementation.
  @param Connection $db the database connection used to execute the query.
  If this parameter is not given, the `db` application component will be used.
  @return int number of records