Information Schema INNODB_METRICS Table

The Information Schema INNODB_METRICS table contains a list of useful InnoDB performance metrics. Each row in the table represents an instrumented counter that can be stopped, started and reset, and which can be grouped together by module.

The PROCESS privilege is required to view the table.

It has the following columns:

Column	Description
Column	Description
NAME	Unique counter name.
SUBSYSTEM	InnoDB subsystem. See below for the matching module to use to enable/disable monitoring this subsytem with the innodb_monitor_enable and innodb_monitor_disable system variables.
COUNT	Count since being enabled.
MAX_COUNT	Maximum value since being enabled.
MIN_COUNT	Minimum value since being enabled.
AVG_COUNT	Average value since being enabled.
COUNT_RESET	Count since last being reset.
MAX_COUNT_RESET	Maximum value since last being reset.
MIN_COUNT_RESET	Minimum value since last being reset.
AVG_COUNT_RESET	Average value since last being reset.
TIME_ENABLED	Time last enabled.
TIME_DISABLED	Time last disabled
TIME_ELAPSED	Time since enabled
TIME_RESET	Time last reset.
ENABLED	1 if enabled, 0 otherwise
TYPE	Item type; one of counter, value, status_counter, set_owner, set_member.
COMMENT	Counter description.

Note: In MariaDB 10.4 and earlier the ENABLED column was called STATUS.

Enabling and Disabling Counters

Most of the counters are disabled by default. To enable them, use the innodb_monitor_enable system variable. You can either enable a variable by its name, for example:

SET GLOBAL innodb_monitor_enable = icp_match;

or enable a number of counters grouped by module. The SUBSYSTEM field indicates which counters are grouped together, but the following module names need to be used:

Module Name	Subsytem Field
Module Name	Subsytem Field
module_metadata	metadata
module_lock	lock
module_buffer	buffer
module_buf_page	buffer_page_io
module_os	os
module_trx	transaction
module_purge	purge
module_compress	compression
module_file	file_system
module_index	index
module_adaptive_hash	adaptive_hash_index From MariaDB 10.6.2, if innodb_adaptive_hash_index is disabled (the default), adaptive_hash_index will not be updated.
module_ibuf_system	change_buffer
module_srv	server
module_ddl	ddl
module_dml	dml
module_log	recovery
module_icp	icp

There are four counters in the icp subsystem:

SELECT NAME, SUBSYSTEM FROM INNODB_METRICS WHERE SUBSYSTEM='icp';
+------------------+-----------+
| NAME             | SUBSYSTEM |
+------------------+-----------+
| icp_attempts     | icp       |
| icp_no_match     | icp       |
| icp_out_of_range | icp       |
| icp_match        | icp       |
+------------------+-----------+

To enable them all, use the associated module name from the table above, module_icp.

SET GLOBAL innodb_monitor_enable = module_icp;

The % wildcard, used to represent any number of characters, can also be used when naming counters, for example:

SET GLOBAL innodb_monitor_enable = 'buffer%'

To disable counters, use the innodb_monitor_disable system variable, using the same naming rules as described above for enabling.

Counter status is not persistent, and will be reset when the server restarts. It is possible to use the options on the command line, or the innodb_monitor_enable option only in a configuration file.

Resetting Counters

Counters can also be reset. Resetting sets all the *_COUNT_RESET values to zero, while leaving the *_COUNT values, which perform counts since the counter was enabled, untouched. Resetting is performed with the innodb_monitor_reset (for individual counters) and innodb_monitor_reset_all (for all counters) system variables.

Simplifying from MariaDB 10.6

MariaDB starting with 10.6

From MariaDB 10.6, the interface was simplified by removing the following:

• buffer_LRU_batches_flush

• buffer_LRU_batch_flush_pages

• buffer_LRU_batches_evict

• buffer_LRU_batch_evict_pages

and by making the following reflect the status variables:

• buffer_LRU_batch_flush_total_pages: innodb_buffer_pool_pages_LRU_flushed

• buffer_LRU_batch_evict_total_pages: innodb_buffer_pool_pages_LRU_freed

The intention is to eventually remove the interface entirely (see MDEV-15706).

Examples

MariaDB 10.8:

SELECT name,subsystem,type,comment FROM INFORMATION_SCHEMA.INNODB_METRICS\G
*************************** 1. row ***************************
     name: metadata_table_handles_opened
subsystem: metadata
     type: counter
  comment: Number of table handles opened
*************************** 2. row ***************************
     name: lock_deadlocks
subsystem: lock
     type: value
  comment: Number of deadlocks
*************************** 3. row ***************************
     name: lock_timeouts
subsystem: lock
     type: value
  comment: Number of lock timeouts
*************************** 4. row ***************************
     name: lock_rec_lock_waits
subsystem: lock
     type: counter
  comment: Number of times enqueued into record lock wait queue
*************************** 5. row ***************************
     name: lock_table_lock_waits
subsystem: lock
     type: counter
  comment: Number of times enqueued into table lock wait queue
*************************** 6. row ***************************
     name: lock_rec_lock_requests
subsystem: lock
     type: counter
  comment: Number of record locks requested
*************************** 7. row ***************************
     name: lock_rec_lock_created
subsystem: lock
     type: counter
  comment: Number of record locks created
*************************** 8. row ***************************
     name: lock_rec_lock_removed
subsystem: lock
     type: counter
  comment: Number of record locks removed from the lock queue
*************************** 9. row ***************************
     name: lock_rec_locks
subsystem: lock
     type: counter
  comment: Current number of record locks on tables
*************************** 10. row ***************************
     name: lock_table_lock_created
subsystem: lock
     type: counter
  comment: Number of table locks created

...

*************************** 207. row ***************************
     name: icp_attempts
subsystem: icp
     type: counter
  comment: Number of attempts for index push-down condition checks
*************************** 208. row ***************************
     name: icp_no_match
subsystem: icp
     type: counter
  comment: Index push-down condition does not match
*************************** 209. row ***************************
     name: icp_out_of_range
subsystem: icp
     type: counter
  comment: Index push-down condition out of range
*************************** 210. row ***************************
     name: icp_match
subsystem: icp
     type: counter
  comment: Index push-down condition matches

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