These views summarize stages, grouped by user. By default, rows are sorted by user and descending total stage latency.
          The user_summary_by_stages and
          x$user_summary_by_stages views
          have these columns:
- user- The client user name. Rows for which the - USERcolumn in the underlying Performance Schema table is- NULLare assumed to be for background threads and are reported with a host name of- background.
- event_name- The stage event name. 
- total- The total number of occurrences of the stage event for the user. 
- total_latency- The total wait time of timed occurrences of the stage event for the user. 
- avg_latency- The average wait time per timed occurrence of the stage event for the user.