28.4.21 The INFORMATION_SCHEMA INNODB_METRICS Table

The INNODB_METRICS table provides a wide variety of InnoDB performance information, complementing the specific focus areas of the Performance Schema tables for InnoDB. With simple queries, you can check the overall health of the system. With more detailed queries, you can diagnose issues such as performance bottlenecks, resource shortages, and application issues.

Each monitor represents a point within the InnoDB source code that is instrumented to gather counter information. Each counter can be started, stopped, and reset. You can also perform these actions for a group of counters using their common module name.

By default, relatively little data is collected. To start, stop, and reset counters, set one of the system variables innodb_monitor_enable, innodb_monitor_disable, innodb_monitor_reset, or innodb_monitor_reset_all, using the name of the counter, the name of the module, a wildcard match for such a name using the “%” character, or the special keyword all.

For usage information, see Section 17.15.6, “InnoDB INFORMATION_SCHEMA Metrics Table”.

The INNODB_METRICS table has these columns:

• NAME

  A unique name for the counter.

• SUBSYSTEM

  The aspect of InnoDB that the metric applies to.

• COUNT

  The value since the counter was enabled.

• MAX_COUNT

  The maximum value since the counter was enabled.

• MIN_COUNT

  The minimum value since the counter was enabled.

• AVG_COUNT

  The average value since the counter was enabled.

• COUNT_RESET

  The counter value since it was last reset. (The _RESET columns act like the lap counter on a stopwatch: you can measure the activity during some time interval, while the cumulative figures are still available in COUNT, MAX_COUNT, and so on.)

• MAX_COUNT_RESET

  The maximum counter value since it was last reset.

• MIN_COUNT_RESET

  The minimum counter value since it was last reset.

• AVG_COUNT_RESET

  The average counter value since it was last reset.

• TIME_ENABLED

  The timestamp of the last start.

• TIME_DISABLED

  The timestamp of the last stop.

• TIME_ELAPSED

  The elapsed time in seconds since the counter started.

• TIME_RESET

  The timestamp of the last reset.

• STATUS

  Whether the counter is still running (enabled) or stopped (disabled).

• TYPE

  Whether the item is a cumulative counter, or measures the current value of some resource.

• COMMENT

  The counter description.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_METRICS WHERE NAME='dml_inserts'\G
*************************** 1. row ***************************
           NAME: dml_inserts
      SUBSYSTEM: dml
          COUNT: 3
      MAX_COUNT: 3
      MIN_COUNT: NULL
      AVG_COUNT: 0.046153846153846156
    COUNT_RESET: 3
MAX_COUNT_RESET: 3
MIN_COUNT_RESET: NULL
AVG_COUNT_RESET: NULL
   TIME_ENABLED: 2014-12-04 14:18:28
  TIME_DISABLED: NULL
   TIME_ELAPSED: 65
     TIME_RESET: NULL
         STATUS: enabled
           TYPE: status_counter
        COMMENT: Number of rows inserted

Notes

• You must have the PROCESS privilege to query this table.

• Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.

• Transaction counter COUNT values may differ from the number of transaction events reported in Performance Schema EVENTS_TRANSACTIONS_SUMMARY tables. InnoDB counts only those transactions that it executes, whereas Performance Schema collects events for all non-aborted transactions initiated by the server, including empty transactions.