MySQL :: MySQL 8.4 Reference Manual :: 15.7.7.16 SHOW ENGINE Statement (original) (raw)

15.7.7.16 SHOW ENGINE Statement

SHOW ENGINE engine_name {STATUS | MUTEX}

SHOW ENGINE displays operational information about a storage engine. It requires thePROCESS privilege. The statement has these variants:

SHOW ENGINE INNODB STATUS
SHOW ENGINE INNODB MUTEX
SHOW ENGINE PERFORMANCE_SCHEMA STATUS

SHOW ENGINE INNODB STATUS displays extensive information from the standard InnoDB Monitor about the state of the InnoDB storage engine. For information about the standard monitor and otherInnoDB Monitors that provide information about InnoDB processing, seeSection 17.17, “InnoDB Monitors”.

SHOW ENGINE INNODB MUTEX displaysInnoDB mutex andrw-lock statistics.

Mutex statistics collection is configured dynamically using the following options:

• To enable the collection of mutex statistics, run:

SET GLOBAL innodb_monitor_enable='latch';  

• To reset mutex statistics, run:

SET GLOBAL innodb_monitor_reset='latch';  

• To disable the collection of mutex statistics, run:

SET GLOBAL innodb_monitor_disable='latch';  

Collection of mutex statistics for SHOW ENGINE INNODB MUTEX can also be enabled by settinginnodb_monitor_enable='all', or disabled by settinginnodb_monitor_disable='all'.

SHOW ENGINE INNODB MUTEX output has these columns:

• Type
  Always InnoDB.
• Name
  For mutexes, the Name field reports only the mutex name. For rwlocks, the Name field reports the source file where the rwlock is implemented, and the line number in the file where the rwlock is created. The line number is specific to your version of MySQL.
• Status
  The mutex status. This field reports the number of spins, waits, and calls. Statistics for low-level operating system mutexes, which are implemented outside ofInnoDB, are not reported.
  • spins indicates the number of spins.
  • waits indicates the number of mutex waits.
  • calls indicates how many times the mutex was requested.

SHOW ENGINE INNODB MUTEX does not list mutexes and rw-locks for each buffer pool block, as the amount of output would be overwhelming on systems with a large buffer pool. SHOW ENGINE INNODB MUTEX does, however, print aggregate BUF_BLOCK_MUTEX spin, wait, and call values for buffer pool block mutexes and rw-locks.SHOW ENGINE INNODB MUTEX also does not list any mutexes or rw-locks that have never been waited on (os_waits=0). Thus, SHOW ENGINE INNODB MUTEX only displays information about mutexes and rw-locks outside of the buffer pool that have caused at least one OS-level wait.

Use SHOW ENGINE PERFORMANCE_SCHEMA STATUS to inspect the internal operation of the Performance Schema code:

mysql> SHOW ENGINE PERFORMANCE_SCHEMA STATUS\G
...
*************************** 3. row ***************************
  Type: performance_schema
  Name: events_waits_history.size
Status: 76
*************************** 4. row ***************************
  Type: performance_schema
  Name: events_waits_history.count
Status: 10000
*************************** 5. row ***************************
  Type: performance_schema
  Name: events_waits_history.memory
Status: 760000
...
*************************** 57. row ***************************
  Type: performance_schema
  Name: performance_schema.memory
Status: 26459600
...

This statement is intended to help the DBA understand the effects that different Performance Schema options have on memory requirements.

Name values consist of two parts, which name an internal buffer and a buffer attribute, respectively. Interpret buffer names as follows:

• An internal buffer that is not exposed as a table is named within parentheses. Examples:(pfs_cond_class).size,(pfs_mutex_class).memory.
• An internal buffer that is exposed as a table in theperformance_schema database is named after the table, without parentheses. Examples:events_waits_history.size,mutex_instances.count.
• A value that applies to the Performance Schema as a whole begins with performance_schema. Example:performance_schema.memory.

Buffer attributes have these meanings:

• size is the size of the internal record used by the implementation, such as the size of a row in a table. size values cannot be changed.
• count is the number of internal records, such as the number of rows in a table.count values can be changed using Performance Schema configuration options.
• For a table,_`tblname`_.memory is the product of size andcount. For the Performance Schema as a whole, performance_schema.memory is the sum of all the memory used (the sum of all othermemory values).

In some cases, there is a direct relationship between a Performance Schema configuration parameter and a SHOW ENGINE value. For example,events_waits_history_long.count corresponds toperformance_schema_events_waits_history_long_size. In other cases, the relationship is more complex. For example,events_waits_history.count corresponds toperformance_schema_events_waits_history_size (the number of rows per thread) multiplied byperformance_schema_max_thread_instances (the number of threads).

SHOW ENGINE NDB STATUS. If the server has the NDB storage engine enabled, SHOW ENGINE NDB STATUS displays cluster status information such as the number of connected data nodes, the cluster connectstring, and cluster binary log epochs, as well as counts of various Cluster API objects created by the MySQL Server when connected to the cluster. Sample output from this statement is shown here:

mysql> SHOW ENGINE NDB STATUS;
+------------+-----------------------+--------------------------------------------------+
| Type       | Name                  | Status                                           |
+------------+-----------------------+--------------------------------------------------+
| ndbcluster | connection            | cluster_node_id=7,
  connected_host=198.51.100.103, connected_port=1186, number_of_data_nodes=4,
  number_of_ready_data_nodes=3, connect_count=0                                         |
| ndbcluster | NdbTransaction        | created=6, free=0, sizeof=212                    |
| ndbcluster | NdbOperation          | created=8, free=8, sizeof=660                    |
| ndbcluster | NdbIndexScanOperation | created=1, free=1, sizeof=744                    |
| ndbcluster | NdbIndexOperation     | created=0, free=0, sizeof=664                    |
| ndbcluster | NdbRecAttr            | created=1285, free=1285, sizeof=60               |
| ndbcluster | NdbApiSignal          | created=16, free=16, sizeof=136                  |
| ndbcluster | NdbLabel              | created=0, free=0, sizeof=196                    |
| ndbcluster | NdbBranch             | created=0, free=0, sizeof=24                     |
| ndbcluster | NdbSubroutine         | created=0, free=0, sizeof=68                     |
| ndbcluster | NdbCall               | created=0, free=0, sizeof=16                     |
| ndbcluster | NdbBlob               | created=1, free=1, sizeof=264                    |
| ndbcluster | NdbReceiver           | created=4, free=0, sizeof=68                     |
| ndbcluster | binlog                | latest_epoch=155467, latest_trans_epoch=148126,
  latest_received_binlog_epoch=0, latest_handled_binlog_epoch=0,
  latest_applied_binlog_epoch=0                                                         |
+------------+-----------------------+--------------------------------------------------+

The Status column in each of these rows provides information about the MySQL server's connection to the cluster and about the cluster binary log's status, respectively. The Status information is in the form of comma-delimited set of name-value pairs.

The connection row'sStatus column contains the name-value pairs described in the following table.

The binlog row'sStatus column contains information relating to NDB Cluster Replication. The name-value pairs it contains are described in the following table.

See Section 25.7, “NDB Cluster Replication”, for more information.

The remaining rows from the output of SHOW ENGINE NDB STATUS which are most likely to prove useful in monitoring the cluster are listed here byName:

• NdbTransaction: The number and size ofNdbTransaction objects that have been created. An NdbTransaction is created each time a table schema operation (such asCREATE TABLE orALTER TABLE) is performed on an NDB table.
• NdbOperation: The number and size ofNdbOperation objects that have been created.
• NdbIndexScanOperation: The number and size of NdbIndexScanOperation objects that have been created.
• NdbIndexOperation: The number and size ofNdbIndexOperation objects that have been created.
• NdbRecAttr: The number and size ofNdbRecAttr objects that have been created. In general, one of these is created each time a data manipulation statement is performed by an SQL node.
• NdbBlob: The number and size ofNdbBlob objects that have been created. An NdbBlob is created for each new operation involving a BLOB column in an NDB table.
• NdbReceiver: The number and size of anyNdbReceiver object that have been created. The number in the created column is the same as the number of data nodes in the cluster to which the MySQL server has connected.

Note

SHOW ENGINE NDB STATUS returns an empty result if no operations involvingNDB tables have been performed during the current session by the MySQL client accessing the SQL node on which this statement is run.