Storage engines

InnoDB

Supports transactions, row-level locking, foreign keys and encryption for tables

[ Variables | Buffer Pool | InnoDB Status ]

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2026-02-03 20:51:21 0x7fdb3811e700 INNODB MONITOR OUTPUT
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Per second averages calculated from the last 49 seconds
-----------------
BACKGROUND THREAD
-----------------
srv_master_thread loops: 26064 srv_active, 0 srv_shutdown, 24207 srv_idle
srv_master_thread log flush and writes: 50267
----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 72544
OS WAIT ARRAY INFO: signal count 60059
RW-shared spins 0, rounds 36349, OS waits 17496
RW-excl spins 0, rounds 9413, OS waits 293
RW-sx spins 195, rounds 1310, OS waits 10
Spin rounds per wait: 36349.00 RW-shared, 9413.00 RW-excl, 6.72 RW-sx
------------------------
LATEST FOREIGN KEY ERROR
------------------------
2026-02-03 10:21:56 0x7fdb38088700 Transaction:
TRANSACTION 64727, ACTIVE 0 sec updating or deleting
mysql tables in use 2, locked 2
4 lock struct(s), heap size 1136, 2 row lock(s), undo log entries 1
MySQL thread id 71236, OS thread handle 140579514648320, query id 2322942 192.168.30.20 root Updating
DELETE FROM `country` WHERE `country`.`country_id` = 1
Foreign key constraint fails for table `sakila`.`city`:
,
  CONSTRAINT `fk_city_country` FOREIGN KEY (`country_id`) REFERENCES `country` (`country_id`) ON UPDATE CASCADE
Trying to delete in parent table, in index PRIMARY tuple:
DATA TUPLE: 5 fields;
 0: len 2; hex 0001; asc   ;;
 1: len 6; hex 00000000fcd7; asc       ;;
 2: len 7; hex 38000001b42e05; asc 8    . ;;
 3: len 11; hex 41666768616e697374616e; asc Afghanistan;;
 4: len 4; hex 43f2a380; asc C   ;;

But in child table `sakila`.`city`, in index idx_fk_country_id, there is a record:
PHYSICAL RECORD: n_fields 2; compact format; info bits 0
 0: len 2; hex 0001; asc   ;;
 1: len 2; hex 00fb; asc   ;;

------------
TRANSACTIONS
------------
Trx id counter 128189
Purge done for trx's n:o < 128189 undo n:o < 0 state: running but idle
History list length 17
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 422054282445304, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 422054282441048, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 422054282436792, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
--------
FILE I/O
--------
I/O thread 0 state: waiting for completed aio requests (insert buffer thread)
I/O thread 1 state: waiting for completed aio requests (log thread)
I/O thread 2 state: waiting for completed aio requests (read thread)
I/O thread 3 state: waiting for completed aio requests (read thread)
I/O thread 4 state: waiting for completed aio requests (read thread)
I/O thread 5 state: waiting for completed aio requests (read thread)
I/O thread 6 state: waiting for completed aio requests (write thread)
I/O thread 7 state: waiting for completed aio requests (write thread)
I/O thread 8 state: waiting for completed aio requests (write thread)
I/O thread 9 state: waiting for completed aio requests (write thread)
Pending normal aio reads: [0, 0, 0, 0] , aio writes: [0, 0, 0, 0] ,
 ibuf aio reads:, log i/o's:, sync i/o's:
Pending flushes (fsync) log: 0; buffer pool: 0
886 OS file reads, 326078 OS file writes, 175138 OS fsyncs
0.00 reads/s, 0 avg bytes/read, 5.16 writes/s, 3.16 fsyncs/s
-------------------------------------
INSERT BUFFER AND ADAPTIVE HASH INDEX
-------------------------------------
Ibuf: size 1, free list len 0, seg size 2, 2 merges
merged operations:
 insert 1, delete mark 1, delete 0
discarded operations:
 insert 0, delete mark 0, delete 0
Hash table size 69257, node heap has 2 buffer(s)
Hash table size 69257, node heap has 11 buffer(s)
Hash table size 69257, node heap has 2 buffer(s)
Hash table size 69257, node heap has 25 buffer(s)
Hash table size 69257, node heap has 1 buffer(s)
Hash table size 69257, node heap has 3 buffer(s)
Hash table size 69257, node heap has 26 buffer(s)
Hash table size 69257, node heap has 0 buffer(s)
2.71 hash searches/s, 0.16 non-hash searches/s
---
LOG
---
Log sequence number 66827084
Log flushed up to   66827084
Pages flushed up to 66827084
Last checkpoint at  66827075
0 pending log flushes, 0 pending chkp writes
106285 log i/o's done, 1.92 log i/o's/second
----------------------
BUFFER POOL AND MEMORY
----------------------
Total large memory allocated 285212672
Dictionary memory allocated 128256
Buffer pool size   16024
Free buffers       15060
Database pages     894
Old database pages 348
Modified db pages  0
Percent of dirty pages(LRU & free pages): 0.000
Max dirty pages percent: 75.000
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 1, not young 0
0.00 youngs/s, 0.00 non-youngs/s
Pages read 727, created 167, written 196488
0.00 reads/s, 0.00 creates/s, 2.84 writes/s
Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s
LRU len: 894, unzip_LRU len: 0
I/O sum[0]:cur[0], unzip sum[0]:cur[0]
--------------
ROW OPERATIONS
--------------
0 queries inside InnoDB, 0 queries in queue
0 read views open inside InnoDB
Process ID=903, Main thread ID=140578733926144, state: sleeping
Number of rows inserted 4, updated 47490, deleted 0, read 2494308
0.00 inserts/s, 0.65 updates/s, 0.00 deletes/s, 1.41 reads/s
Number of system rows inserted 0, updated 0, deleted 0, read 14480
0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s
----------------------------
END OF INNODB MONITOR OUTPUT
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