Storage engines
InnoDB
Supports transactions, row-level locking, foreign keys and encryption for tables
[
Variables
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Buffer Pool
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InnoDB Status
]
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2026-03-22 18:19:50 0x7f802c1986c0 INNODB MONITOR OUTPUT
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Per second averages calculated from the last 5 seconds
-----------------
BACKGROUND THREAD
-----------------
srv_master_thread loops: 44695 srv_active, 0 srv_shutdown, 13599293 srv_idle
srv_master_thread log flush and writes: 13643833
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SEMAPHORES
----------
OS WAIT ARRAY INFO: reservation count 350363
OS WAIT ARRAY INFO: signal count 195939
RW-shared spins 36109, rounds 826113, OS waits 26511
RW-excl spins 30668, rounds 208549, OS waits 1702
RW-sx spins 351, rounds 6352, OS waits 130
Spin rounds per wait: 22.88 RW-shared, 6.80 RW-excl, 18.10 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 ;;
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TRANSACTIONS
------------
Trx id counter 1133753
Purge done for trx's n:o < 1133753 undo n:o < 0 state: running but idle
History list length 4
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 421663507551192, 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 421663507546976, 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 421663507525896, not started flushing log
mysql tables in use 1, locked 1
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 421663507568056, not started
0 lock struct(s), heap size 1128, 0 row lock(s)
---TRANSACTION 421663507559624, 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 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
327374 OS file reads, 577093 OS file writes, 307727 OS fsyncs
3.00 reads/s, 16384 avg bytes/read, 4.00 writes/s, 3.40 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 1 buffer(s)
10.80 hash searches/s, 39.19 non-hash searches/s
---
LOG
---
Log sequence number 317309038
Log flushed up to 317309038
Pages flushed up to 317296170
Last checkpoint at 317293657
0 pending log flushes, 0 pending chkp writes
162908 log i/o's done, 2.80 log i/o's/second
----------------------
BUFFER POOL AND MEMORY
----------------------
Total large memory allocated 33554432
Dictionary memory allocated 261080
Buffer pool size 1003
Free buffers 737
Database pages 258
Old database pages 0
Modified db pages 27
Percent of dirty pages(LRU & free pages): 2.711
Max dirty pages percent: 75.000
Pending reads 0
Pending writes: LRU 0, flush list 0, single page 0
Pages made young 103, not young 81820
0.00 youngs/s, 0.00 non-youngs/s
Pages read 327265, created 4071, written 365915
3.00 reads/s, 0.00 creates/s, 1.00 writes/s
Buffer pool hit rate 974 / 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: 258, unzip_LRU len: 0
I/O sum[336]:cur[5], 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 68219, updated 59638, deleted 2051, read 318825136
0.00 inserts/s, 2.40 updates/s, 0.00 deletes/s, 10.80 reads/s
Number of system rows inserted 0, updated 0, deleted 0, read 168106
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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