29.12.20.11 Error Summary Tables

The Performance Schema maintains summary tables for aggregating statistical information about server errors (and warnings). For a list of server errors, see Server Error Message Reference.

Collection of error information is controlled by the error instrument, which is enabled by default. Timing information is not collected.

Each error summary table has three columns that identify the error:

ERROR_NUMBER is the numeric error value. The value is unique.
ERROR_NAME is the symbolic error name corresponding to the ERROR_NUMBER value. The value is unique.
SQLSTATE is the SQLSTATE value corresponding to the ERROR_NUMBER value. The value is not necessarily unique.

For example, if ERROR_NUMBER is 1050, ERROR_NAME is ER_TABLE_EXISTS_ERROR and SQLSTATE is 42S01.

Example error event summary information:

mysql> SELECT *
       FROM performance_schema.events_errors_summary_global_by_error
       WHERE SUM_ERROR_RAISED <> 0\G
*************************** 1. row ***************************
     ERROR_NUMBER: 1064
       ERROR_NAME: ER_PARSE_ERROR
        SQL_STATE: 42000
 SUM_ERROR_RAISED: 1
SUM_ERROR_HANDLED: 0
       FIRST_SEEN: 2016-06-28 07:34:02
        LAST_SEEN: 2016-06-28 07:34:02
*************************** 2. row ***************************
     ERROR_NUMBER: 1146
       ERROR_NAME: ER_NO_SUCH_TABLE
        SQL_STATE: 42S02
 SUM_ERROR_RAISED: 2
SUM_ERROR_HANDLED: 0
       FIRST_SEEN: 2016-06-28 07:34:05
        LAST_SEEN: 2016-06-28 07:36:18
*************************** 3. row ***************************
     ERROR_NUMBER: 1317
       ERROR_NAME: ER_QUERY_INTERRUPTED
        SQL_STATE: 70100
 SUM_ERROR_RAISED: 1
SUM_ERROR_HANDLED: 0
       FIRST_SEEN: 2016-06-28 11:01:49
        LAST_SEEN: 2016-06-28 11:01:49

Each error summary table has one or more grouping columns to indicate how the table aggregates errors:

events_errors_summary_by_account_by_error has USER, HOST, and ERROR_NUMBER columns. Each row summarizes events for a given account (user and host combination) and error.
events_errors_summary_by_host_by_error has HOST and ERROR_NUMBER columns. Each row summarizes events for a given host and error.
events_errors_summary_by_thread_by_error has THREAD_ID and ERROR_NUMBER columns. Each row summarizes events for a given thread and error.
events_errors_summary_by_user_by_error has USER and ERROR_NUMBER columns. Each row summarizes events for a given user and error.
events_errors_summary_global_by_error has an ERROR_NUMBER column. Each row summarizes events for a given error.

Each error summary table has these summary columns containing aggregated values:

SUM_ERROR_RAISED
This column aggregates the number of times the error occurred.
SUM_ERROR_HANDLED
This column aggregates the number of times the error was handled by an SQL exception handler.
FIRST_SEEN, LAST_SEEN
Timestamp indicating when the error was first seen and most recently seen.

A NULL row in each error summary table is used to aggregate statistics for all errors that lie out of range of the instrumented errors. For example, if MySQL Server errors lie in the range from M to N and an error is raised with number Q not in that range, the error is aggregated in the NULL row. The NULL row is the row with ERROR_NUMBER=0, ERROR_NAME=NULL, and SQLSTATE=NULL.

The error summary tables have these indexes:

events_errors_summary_by_account_by_error:
- Primary key on (USER, HOST, ERROR_NUMBER)
events_errors_summary_by_host_by_error:
- Primary key on (HOST, ERROR_NUMBER)
events_errors_summary_by_thread_by_error:
- Primary key on (THREAD_ID, ERROR_NUMBER)
events_errors_summary_by_user_by_error:
- Primary key on (USER, ERROR_NUMBER)
events_errors_summary_global_by_error:
- Primary key on (ERROR_NUMBER)

TRUNCATE TABLE is permitted for error summary tables. It has these effects:

For summary tables not aggregated by account, host, or user, truncation resets the summary columns to zero or NULL rather than removing rows.
For summary tables aggregated by account, host, or user, truncation removes rows for accounts, hosts, or users with no connections, and resets the summary columns to zero or NULL for the remaining rows.

In addition, each error summary table that is aggregated by account, host, user, or thread is implicitly truncated by truncation of the connection table on which it depends, or truncation of events_errors_summary_global_by_error. For details, see Section 29.12.8, “Performance Schema Connection Tables”.