code: def _query_by_system(self, table_name):
          
          logger.info('Querying for downloads by system in table %s',
                      table_name)
          q = "SELECT file.project, details.system.name, COUNT(*) as dl_count " \
              "%s " \
              "%s " \
              "GROUP BY file.project, details.system.name;" % (
                  self._from_for_table(table_name),
                  self._where_for_projects
              )
          res = self._run_query(q)
          result = self._dict_for_projects()
          for row in res:
              system = row['details_system_name']
              result[row['file_project']][system] = int(
                  row['dl_count'])
          return result
docs: Query for download data broken down by system, for one day.
  
          :param table_name: table name to query against
          :type table_name: str
          :return: dict of download information by system; keys are project name,
            values are a dict of system names to download count.
          :rtype: dict