Storage engines

InnoDB

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

[ Variables | Buffer Pool | InnoDB Status ]

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2026-01-21 16:37:30 0x7f803e6886c0 INNODB MONITOR OUTPUT
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Per second averages calculated from the last 13 seconds
-----------------
BACKGROUND THREAD
-----------------
srv_master_thread loops: 26477 srv_active, 0 srv_shutdown, 8428937 srv_idle
srv_master_thread log flush and writes: 8455318
----------
SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 177497
OS WAIT ARRAY INFO: signal count 97479
RW-shared spins 18997, rounds 446981, OS waits 14347
RW-excl spins 15960, rounds 112392, OS waits 906
RW-sx spins 195, rounds 4347, OS waits 94
Spin rounds per wait: 23.53 RW-shared, 7.04 RW-excl, 22.29 RW-sx
------------------------
LATEST FOREIGN KEY ERROR
------------------------
2025-10-16 07:42:35 0x7f803e7ff6c0 Transaction:
TRANSACTION 827757, ACTIVE 0 sec inserting
mysql tables in use 1, locked 1
3 lock struct(s), heap size 1128, 1 row lock(s), undo log entries 1
MySQL thread id 54, OS thread handle 140188781115072, query id 1109 localhost ::1 root Update
-- Question 1: Пол
INSERT INTO questions (survey_id, group_id, question_text, question_type_id, position)
VALUES (@survey_id, 1, 'У коју средњу школу идете (ПИТАЊЕ САМО ЗА УЧЕНИКЕ):', 1, 1)
Foreign key constraint fails for table `surveys`.`questions`:
,
  CONSTRAINT `questions_ibfk_1` FOREIGN KEY (`survey_id`) REFERENCES `survey` (`id`) in parent table, in index survey_id tuple:
DATA TUPLE: 2 fields;
 0: len 4; hex 80000006; asc     ;;
 1: len 4; hex 80000007; asc     ;;

But in parent table `surveys`.`survey`, in index PRIMARY,
the closest match we can find is record:
PHYSICAL RECORD: n_fields 13; compact format; info bits 0
 0: len 4; hex 80000002; asc     ;;
 1: len 6; hex 000000000000; asc       ;;
 2: len 7; hex 80000000000000; asc        ;;
 3: len 30; hex 376532623463356638643961306231326333643465366637383930616263; asc 7e2b4c5f8d9a0b12c3d4e6f7890abc; (total 32 bytes);
 4: len 30; hex d094d0b8d0b3d0b8d182d0b0d0bbd0bdd0b020d0b7d0b4d180d0b0d0b2d1; asc                               ; (total 60 bytes);
 5: len 30; hex d0a3d0bfd0b8d182d0bdd0b8d0ba20d0be20d0b4d0b8d0b3d0b8d182d0b0; asc                               ; (total 540 bytes);
 6: len 30; hex d096d0b5d0bbd0b8d0bcd0be20d0b4d0b020d0b1d0bed199d0b520d180d0; asc                               ; (total 709 bytes);
 7: len 30; hex d092d0b0d188d0b520d0bcd0b8d188d199d0b5d19ad0b520d0bdd0b0d0bc; asc                               ; (total 445 bytes);
 8: len 4; hex 8000000a; asc     ;;
 9: len 4; hex 68f085cb; asc h   ;;
 10: len 4; hex 692b7af0; asc i+z ;;
 11: len 6; hex 616374697665; asc active;;
 12: len 4; hex 80000002; asc     ;;

------------
TRANSACTIONS
------------
Trx id counter 1017608
Purge done for trx's n:o < 1017608 undo n:o < 0 state: running but idle
History list length 7
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 421663507559624, not started
0 lock struct(s), heap size 1128, 0 row lock(s)
---TRANSACTION 421663507555408, not started
0 lock struct(s), heap size 1128, 0 row lock(s)
---TRANSACTION 421663507551192, not started
0 lock struct(s), heap size 1128, 0 row lock(s)
---TRANSACTION 421663507546976, not started
0 lock struct(s), heap size 1128, 0 row lock(s)
---TRANSACTION 421663507534328, not started
0 lock struct(s), heap size 1128, 0 row lock(s)
---TRANSACTION 421663507530112, not started
0 lock struct(s), heap size 1128, 0 row lock(s)
---TRANSACTION 421663507542760, not started
0 lock struct(s), heap size 1128, 0 row lock(s)
---TRANSACTION 421663507538544, not started
0 lock struct(s), heap size 1128, 0 row lock(s)
---TRANSACTION 421663507525896, not started
0 lock struct(s), heap size 1128, 0 row lock(s)
---TRANSACTION 421663507521680, not started
0 lock struct(s), heap size 1128, 0 row lock(s)
--------
FILE I/O
--------
I/O thread 0 state: waiting for i/o request (insert buffer thread)
I/O thread 1 state: waiting for i/o request (log thread)
I/O thread 2 state: waiting for i/o request (read thread)
I/O thread 3 state: waiting for i/o request (read thread)
I/O thread 4 state: waiting for i/o request (read thread)
I/O thread 5 state: waiting for i/o request (read thread)
I/O thread 6 state: waiting for i/o request (write thread)
I/O thread 7 state: waiting for i/o request (write thread)
I/O thread 8 state: waiting for i/o request (write thread)
I/O thread 9 state: waiting for i/o request (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
181290 OS file reads, 358530 OS file writes, 187166 OS fsyncs
3.31 reads/s, 16384 avg bytes/read, 15.15 writes/s, 5.46 fsyncs/s
-------------------------------------
INSERT BUFFER AND ADAPTIVE HASH INDEX
-------------------------------------
Ibuf: size 1, free list len 3, seg size 5, 5 merges
merged operations:
 insert 0, delete mark 12, delete 7
discarded operations:
 insert 0, delete mark 0, delete 0
Hash table size 4441, node heap has 1 buffer(s)
Hash table size 4441, node heap has 1 buffer(s)
Hash table size 4441, node heap has 1 buffer(s)
Hash table size 4441, node heap has 1 buffer(s)
Hash table size 4441, node heap has 1 buffer(s)
Hash table size 4441, node heap has 1 buffer(s)
Hash table size 4441, node heap has 1 buffer(s)
Hash table size 4441, node heap has 2 buffer(s)
43.30 hash searches/s, 52.61 non-hash searches/s
---
LOG
---
Log sequence number 280952880
Log flushed up to   280952860
Pages flushed up to 280948023
Last checkpoint at  280901207
0 pending log flushes, 0 pending chkp writes
99907 log i/o's done, 3.69 log i/o's/second
----------------------
BUFFER POOL AND MEMORY
----------------------
Total large memory allocated 33554432
Dictionary memory allocated 261080
Buffer pool size   1003
Free buffers       738
Database pages     256
Old database pages 0
Modified db pages  9
Percent of dirty pages(LRU & free pages): 0.905
Max dirty pages percent: 75.000
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 74, not young 51118
0.00 youngs/s, 0.00 non-youngs/s
Pages read 181181, created 2739, written 229132
3.31 reads/s, 0.08 creates/s, 10.77 writes/s
Buffer pool hit rate 987 / 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: 256, unzip_LRU len: 0
I/O sum[183]: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=37828, Main thread ID=140188135192256, state: sleeping
Number of rows inserted 38359, updated 35616, deleted 979, read 136587669
0.00 inserts/s, 3.31 updates/s, 0.00 deletes/s, 30.46 reads/s
Number of system rows inserted 0, updated 0, deleted 0, read 104899
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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