Bug #68768 MIN_TIMER_WAIT in events_waits_summary_global_by_event_name overflows

• Submitted: 25 Mar 2013 21:28
• Modified: 9 Apr 2013 14:25
• Reporter: Vadim Tkachenko
• Status: Closed
• Category: MySQL Server: Performance Schema
• Severity: S3 (Non-critical)
• OS: Any
• Assigned to: Marc ALFF
• CPU Architecture: Any

[25 Mar 2013 21:28] Vadim Tkachenko

Description:
I just started mysqld with
performance_schema_instrument='wait/%=counted'

and run following query.
mysql> select * from events_waits_summary_global_by_event_name;
+------------------------------------------------------------+------------+-----------------+----------------------+----------------+-----------------+
| EVENT_NAME                                                 | COUNT_STAR | SUM_TIMER_WAIT  | MIN_TIMER_WAIT       | AVG_TIMER_WAIT | MAX_TIMER_WAIT  |
+------------------------------------------------------------+------------+-----------------+----------------------+----------------+-----------------+
| wait/synch/mutex/sql/hash_filo::lock                       |          2 |               0 | 18446744073709551147 |              0 |               0 |
| wait/synch/mutex/sql/LOCK_connection_count                 |          1 |               0 | 18446744073709551147 |              0 |               0 |

It seems MIN_TIMER_WAIT  is too big to be correct

How to repeat:
run select * from events_waits_summary_global_by_event_name;

Suggested fix:
use 0 instead of 18446744073709551147

[26 Mar 2013 8:00] MySQL Verification Team

Hello VADYM,

Thank you for the report.
Verified as described.

5.6.10
========

Started mysqld with performance_schema_instrument='wait/%=counted'

mysql> select * from events_waits_summary_global_by_event_name;
+------------------------------------------------------------+------------+------------------+----------------------+----------------+------------------+
| EVENT_NAME                                                 | COUNT_STAR | SUM_TIMER_WAIT   | MIN_TIMER_WAIT       | AVG_TIMER_WAIT | MAX_TIMER_WAIT   |
+------------------------------------------------------------+------------+------------------+----------------------+----------------+------------------+
| wait/synch/mutex/sql/hash_filo::lock                       |          2 |                0 | 18446744073709551225 |              0 |                0 |
| wait/synch/mutex/sql/LOCK_connection_count                 |          1 |                0 | 18446744073709551225 |              0 |                0 |

Thanks,
Umesh

[9 Apr 2013 8:48] Marc ALFF

Thanks Vadym.

[9 Apr 2013 14:25] Paul DuBois

Noted in 5.6.12, 5.7.2 changelogs.

When only counting events but not timing them, Performance Schema
would report MIN_TIMER_WAIT values as a large number instead of 0.