def purge_by_date(older_than, window = nil, &block)
      _log.info("Purging #{table_name.humanize} older than [#{older_than}]...")
      total = purge_in_batches(purge_scope(older_than), window || purge_window_size, &block)
      _log.info("Purging #{table_name.humanize} older than [#{older_than}]...Complete - Deleted #{total} records")
      total