code: protected function loadTablePrimaryKey($tableName)
      {
          $primaryKey = $this->db->getSlavePdo()->cubrid_schema(\PDO::CUBRID_SCH_PRIMARY_KEY, $tableName);
          if (empty($primaryKey)) {
              return null;
          }
  
          ArrayHelper::multisort($primaryKey, 'KEY_SEQ', SORT_ASC, SORT_NUMERIC);
          return new Constraint([
              'name' => $primaryKey[0]['KEY_NAME'],
              'columnNames' => ArrayHelper::getColumn($primaryKey, 'ATTR_NAME'),
          ]);
      }
docs: {@inheritdoc}