Extended show engine InnoDB status¶

This feature reorganizes the output of SHOW ENGINE INNODB STATUS to improve readability and to provide additional information. The variable innodb_show_locks_held controls the umber of locks held to print for each InnoDB transaction.

This feature modified the SHOW ENGINE INNODB STATUS command as follows:

Added extended information about InnoDB internal hash table sizes (in bytes) in the BUFFER POOL AND MEMORY section; also added buffer pool size in bytes.
Added additional LOG section information.

Other information¶

Author / Origin: Baron Schwartz, https://lists.mysql.com/internals/35174

System variables¶

`innodb_show_locks_held`¶

Option	Description
Command-line	Yes
Config file	Yes
Scope	Global
Dynamic	Yes
Data type	ULONG
Default	10
Range	0 - 1000

Specifies the number of locks held to print for each InnoDB transaction in SHOW ENGINE INNODB STATUS.

`innodb_print_lock_wait_timeout_info`¶

Option	Description
Command-line	Yes
Config file	Yes
Scope	Global
Dynamic	Yes
Data type	Boolean
Default	OFF

Makes InnoDB to write information about all lock wait timeout errors into the log file.

This allows to find out details about the failed transaction, and, most importantly, the blocking transaction. Query string can be obtained from EVENTS_STATEMENTS_CURRENT table, based on the PROCESSLIST_ID field, which corresponds to thread_id from the log output.

Taking into account that blocking transaction is often a multiple statement one, following query can be used to obtain blocking thread statements history:

SELECT s.SQL_TEXT FROM performance_schema.events_statements_history s
INNER JOIN performance_schema.threads t ON t.THREAD_ID = s.THREAD_ID
WHERE t.PROCESSLIST_ID = %d
UNION
SELECT s.SQL_TEXT FROM performance_schema.events_statements_current s
INNER JOIN performance_schema.threads t ON t.THREAD_ID = s.THREAD_ID
WHERE t.PROCESSLIST_ID = %d;

The PROCESSLIST_ID in this example is exactly the thread id from error log output.

Status variables¶

The status variables here contain information available in the output of SHOW ENGINE INNODB STATUS, organized by the sections SHOW ENGINE INNODB STATUS displays. If you are familiar with the output of SHOW ENGINE INNODB STATUS, you will probably already recognize the information these variables contain.

BACKGROUND THREAD¶

The following variables contain information in the BACKGROUND THREAD section of the output from SHOW ENGINE INNODB STATUS.

Expected output

-----------------
BACKGROUND THREAD
-----------------
srv_master_thread loops: 1 srv_active, 0 srv_shutdown, 11844 srv_idle
srv_master_thread log flush and writes: 11844

InnoDB has a source thread which performs background tasks depending on the server state, once per second. If the server is under workload, the source thread runs the following: performs background table drops; performs change buffer merge, adaptively; flushes the redo log to disk; evicts tables from the dictionary cache if needed to satisfy its size limit; makes a checkpoint. If the server is idle: performs background table drops, flushes and/or checkpoints the redo log if needed due to the checkpoint age; performs change buffer merge at full I/O capacity; evicts tables from the dictionary cache if needed; and makes a checkpoint.

`Innodb_master_thread_active_loops`¶

Option	Description
Scope	Global
Data type	Numeric

This variable shows the number of times the above one-second loop was executed for active server states.

`Innodb_master_thread_idle_loops`¶

Option	Description
Scope	Global
Data type	Numeric

This variable shows the number of times the above one-second loop was executed for idle server states.

`Innodb_background_log_sync`¶

Option	Description
Scope	Global
Data type	Numeric

This variable shows the number of times the InnoDB source thread has written and flushed the redo log.

SEMAPHORES¶

The following variables contain information in the SEMAPHORES section of the output from SHOW ENGINE INNODB STATUS. An example of that output is:

Expected output

----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 9664, signal count 11182
Mutex spin waits 20599, rounds 223821, OS waits 4479
RW-shared spins 5155, OS waits 1678; RW-excl spins 5632, OS waits 2592
Spin rounds per wait: 10.87 mutex, 15.01 RW-shared, 27.19 RW-excl

INSERT BUFFER AND ADAPTIVE HASH INDEX¶

The following variables contain information in the INSERT BUFFER AND ADAPTIVE HASH INDEX section of the output from SHOW ENGINE INNODB STATUS. An example of that output is:

Expected output

-------------------------------------
INSERT BUFFER AND ADAPTIVE HASH INDEX
-------------------------------------
Ibuf: size 1, free list len 6089, seg size 6091,
44497 inserts, 44497 merged recs, 8734 merges
0.00 hash searches/s, 0.00 non-hash searches/s

`Innodb_ibuf_free_list`¶

Option	Description
Scope	Global
Data type	Numeric

`Innodb_ibuf_segment_size`¶

Option	Description
Scope	Global
Data type	Numeric

LOG¶

The following variables contain information in the LOG section of the output from SHOW ENGINE INNODB STATUS. An example of that output is:

Expected output

LOG
---
Log sequence number 10145937666
Log flushed up to   10145937666
Pages flushed up to 10145937666
Last checkpoint at  10145937666
Max checkpoint age    80826164
Checkpoint age target 78300347
Modified age          0
Checkpoint age        0
0 pending log writes, 0 pending chkp writes
9 log i/o's done, 0.00 log i/o's/second
Log tracking enabled
Log tracked up to   10145937666
Max tracked LSN age 80826164

`Innodb_lsn_current`¶

Option	Description
Scope	Global
Data type	Numeric

This variable shows the current log sequence number.

`Innodb_lsn_flushed`¶

Option	Description
Scope	Global
Data type	Numeric

This variable shows the current maximum LSN that has been written and flushed to disk.

`Innodb_lsn_last_checkpoint`¶

Option	Description
Scope	Global
Data type	Numeric

This variable shows the LSN of the latest completed checkpoint.

`Innodb_checkpoint_age`¶

Option	Description
Scope	Global
Data type	Numeric

This variable shows the current InnoDB checkpoint age, i.e., the difference between the current LSN and the LSN of the last completed checkpoint.

`Innodb_checkpoint_max_age`¶

Option	Description
Scope	Global
Data type	Numeric

This variable shows the maximum allowed checkpoint age above which the redo log is close to full and a checkpoint must happen before any further redo log writes.

Note

This variable was removed in Percona Server for MySQL 8.0.13-4 due to a change in MySQL. The variable is identical to log capacity.

BUFFER POOL AND MEMORY¶

The following variables contain information in the BUFFER POOL AND MEMORY section of the output from SHOW ENGINE INNODB STATUS. An example of that output is:

Expected output

----------------------
BUFFER POOL AND MEMORY
----------------------
Total memory allocated 137363456; in additional pool allocated 0
Total memory allocated by read views 88
Internal hash tables (constant factor + variable factor)
    Adaptive hash index 2266736         (2213368 + 53368)
    Page hash           139112 (buffer pool 0 only)
    Dictionary cache    729463  (554768 + 174695)
    File system         824800  (812272 + 12528)
    Lock system         333248  (332872 + 376)
    Recovery system     0       (0 + 0)
Dictionary memory allocated 174695
Buffer pool size        8191
Buffer pool size, bytes 134201344
Free buffers            7481
Database pages          707
Old database pages      280
Modified db pages       0
Pending reads 0
Pending writes: LRU 0, flush list 0 single page 0
Pages made young 0, not young 0
0.00 youngs/s, 0.00 non-youngs/s
Pages read 707, created 0, written 1
0.00 reads/s, 0.00 creates/s, 0.00 writes/s
No buffer pool page gets since the last printout
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 707, unzip_LRU len: 0

`Innodb_mem_adaptive_hash`¶

Option	Description
Scope	Global
Data type	Numeric

This variable shows the current size, in bytes, of the adaptive hash index.

`Innodb_mem_dictionary`¶

Option	Description
Scope	Global
Data type	Numeric

This variable shows the current size, in bytes, of the InnoDB in-memory data dictionary info.

`Innodb_mem_total`¶

Option	Description
Scope	Global
Data type	Numeric

This variable shows the total amount of memory, in bytes, InnoDB has allocated in the process heap memory.

`Innodb_buffer_pool_pages_LRU_flushed`¶

Option	Description
Scope	Global
Data type	Numeric

This variable shows the total number of buffer pool pages which have been flushed from the LRU list, i.e., too old pages which had to be flushed in order to make buffer pool room to read in new data pages.

`Innodb_buffer_pool_pages_made_not_young`¶

Option	Description
Scope	Global
Data type	Numeric

This variable shows the number of times a buffer pool page was not marked as accessed recently in the LRU list because of innodb_old_blocks_time variable setting.

`Innodb_buffer_pool_pages_made_young`¶

Option	Description
Scope	Global
Data type	Numeric

This variable shows the number of times a buffer pool page was moved to the young end of the LRU list due to its access, to prevent its eviction from the buffer pool.

`Innodb_buffer_pool_pages_old`¶

Option	Description
Scope	Global
Data type	Numeric

This variable shows the total number of buffer pool pages which are considered to be old according to the Making the Buffer Pool Scan Resistant manual page.

TRANSACTIONS¶

The following variables contain information in the TRANSACTIONS section of the output from SHOW INNODB STATUS. An example of that output is:

Expected output

------------
TRANSACTIONS
------------
Trx id counter F561FD
Purge done for trx's n:o < F561EB undo n:o < 0
History list length 19
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 0, not started, process no 993, OS thread id 140213152634640
mysql thread id 15933, query id 32109 localhost root
show innodb status
---TRANSACTION F561FC, ACTIVE 29 sec, process no 993, OS thread id 140213152769808 updating or deleting
mysql tables in use 1, locked 1

`Innodb_max_trx_id`¶

Option	Description
Scope	Global
Data type	Numeric

This variable shows the next free transaction id number.

`Innodb_oldest_view_low_limit_trx_id`¶

Option	Description
Scope	Global
Data type	Numeric

This variable shows the highest transaction id, above which the current oldest open read view does not see any transaction changes. Zero if there is no open view.

`Innodb_purge_trx_id`¶

Option	Description
Scope	Global
Data type	Numeric

This variable shows the oldest transaction id whose records have not been purged yet.

`Innodb_purge_undo_no`¶

Option	Description
Scope	Global
Data type	Numeric

INFORMATION_SCHEMA Tables¶

The following table contains information about the oldest active transaction in the system.

`INFORMATION_SCHEMA.XTRADB_READ_VIEW`¶

Column Name	Description
‘READ_VIEW_LOW_LIMIT_TRX_NUMBER’	This is the highest transactions number at the time the view was created.
‘READ_VIEW_UPPER_LIMIT_TRX_ID’	This is the highest transactions ID at the time the view was created. This means that it should not see newer transactions with IDs bigger than or equal to that value.
‘READ_VIEW_LOW_LIMIT_TRX_ID’	This is the latest committed transaction ID at the time the oldest view was created. This means that it should see all transactions with IDs smaller than or equal to that value.

Note

Starting with Percona Server for MySQL 8.0.20-11, in INFORMATION_SCHEMA.XTRADB_READ_VIEW, the data type for the following columns is changed from VARCHAR(18) to BIGINT UNSIGNED:

READ_VIEW_LOW_LIMIT_TRX_NUMBER
READ_VIEW_UPPER_LIMIT_TRX_ID
READ_VIWE_LOW_LIMIT_TRX_ID

The columns contain 64-bit integers, which is too large for VARCHAR(18).

The following table contains information about the memory usage for InnoDB/XtraDB hash tables.

`INFORMATION_SCHEMA.XTRADB_INTERNAL_HASH_TABLES`¶

Column Name	Description
‘INTERNAL_HASH_TABLE_NAME’	Hash table name
‘TOTAL_MEMORY’	Total amount of memory
‘CONSTANT_MEMORY’	Constant memory
‘VARIABLE_MEMORY’	Variable memory

Extended show engine InnoDB status¶

Other information¶

System variables¶

`innodb_show_locks_held`¶

`innodb_print_lock_wait_timeout_info`¶

Status variables¶

BACKGROUND THREAD¶

`Innodb_master_thread_active_loops`¶

`Innodb_master_thread_idle_loops`¶

`Innodb_background_log_sync`¶

SEMAPHORES¶

INSERT BUFFER AND ADAPTIVE HASH INDEX¶

`Innodb_ibuf_free_list`¶

`Innodb_ibuf_segment_size`¶

LOG¶

`Innodb_lsn_current`¶

`Innodb_lsn_flushed`¶

`Innodb_lsn_last_checkpoint`¶

`Innodb_checkpoint_age`¶

`Innodb_checkpoint_max_age`¶

BUFFER POOL AND MEMORY¶

`Innodb_mem_adaptive_hash`¶

`Innodb_mem_dictionary`¶

`Innodb_mem_total`¶

`Innodb_buffer_pool_pages_LRU_flushed`¶

`Innodb_buffer_pool_pages_made_not_young`¶

`Innodb_buffer_pool_pages_made_young`¶

`Innodb_buffer_pool_pages_old`¶

TRANSACTIONS¶

`Innodb_max_trx_id`¶

`Innodb_oldest_view_low_limit_trx_id`¶

`Innodb_purge_trx_id`¶

`Innodb_purge_undo_no`¶

INFORMATION_SCHEMA Tables¶

`INFORMATION_SCHEMA.XTRADB_READ_VIEW`¶

`INFORMATION_SCHEMA.XTRADB_INTERNAL_HASH_TABLES`¶

Other reading¶

Contact us

Extended show engine InnoDB status¶

Other information¶

System variables¶

innodb_show_locks_held¶

innodb_print_lock_wait_timeout_info¶

Status variables¶

BACKGROUND THREAD¶

Innodb_master_thread_active_loops¶

Innodb_master_thread_idle_loops¶

Innodb_background_log_sync¶

SEMAPHORES¶

INSERT BUFFER AND ADAPTIVE HASH INDEX¶

Innodb_ibuf_free_list¶

Innodb_ibuf_segment_size¶

LOG¶

Innodb_lsn_current¶

Innodb_lsn_flushed¶

Innodb_lsn_last_checkpoint¶

Innodb_checkpoint_age¶

Innodb_checkpoint_max_age¶

BUFFER POOL AND MEMORY¶

Innodb_mem_adaptive_hash¶

Innodb_mem_dictionary¶

Innodb_mem_total¶

Innodb_buffer_pool_pages_LRU_flushed¶

Innodb_buffer_pool_pages_made_not_young¶

Innodb_buffer_pool_pages_made_young¶

Innodb_buffer_pool_pages_old¶

TRANSACTIONS¶

Innodb_max_trx_id¶

Innodb_oldest_view_low_limit_trx_id¶

Innodb_purge_trx_id¶

Innodb_purge_undo_no¶

INFORMATION_SCHEMA Tables¶

INFORMATION_SCHEMA.XTRADB_READ_VIEW¶

INFORMATION_SCHEMA.XTRADB_INTERNAL_HASH_TABLES¶

Other reading¶

Contact us

`innodb_show_locks_held`¶

`innodb_print_lock_wait_timeout_info`¶

`Innodb_master_thread_active_loops`¶

`Innodb_master_thread_idle_loops`¶

`Innodb_background_log_sync`¶

`Innodb_ibuf_free_list`¶

`Innodb_ibuf_segment_size`¶

`Innodb_lsn_current`¶

`Innodb_lsn_flushed`¶

`Innodb_lsn_last_checkpoint`¶

`Innodb_checkpoint_age`¶

`Innodb_checkpoint_max_age`¶

`Innodb_mem_adaptive_hash`¶

`Innodb_mem_dictionary`¶

`Innodb_mem_total`¶

`Innodb_buffer_pool_pages_LRU_flushed`¶

`Innodb_buffer_pool_pages_made_not_young`¶

`Innodb_buffer_pool_pages_made_young`¶

`Innodb_buffer_pool_pages_old`¶

`Innodb_max_trx_id`¶

`Innodb_oldest_view_low_limit_trx_id`¶

`Innodb_purge_trx_id`¶

`Innodb_purge_undo_no`¶

`INFORMATION_SCHEMA.XTRADB_READ_VIEW`¶

`INFORMATION_SCHEMA.XTRADB_INTERNAL_HASH_TABLES`¶