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Results tagged with mysql
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user 69194
All versions of MySQL (not Microsoft SQL Server). Please also add a version-specific tag like mysql-5.7 if that is relevant to the question.
6
votes
Accepted
MySQL: What does event `/io/table/sql/handler` mean?
examples:
io/table/sql/handler = storage engine is processing an I/O request against a table
lock/table/sql/handler = storage engine is processing a table lock operation
Reference
See the MySQL …
- 523
7
votes
1
answer
29k
views
MySQL: What does event `/io/table/sql/handler` mean?
Yesterday I experienced a MySQL incident
the load was extremely high
All select statements takes more than 3 times time than usual.
All insert statements takes 10+ times time than usual. … The MySQL performance monitor tool shows:
there are lots of /io/table/sql/handler has been generated during the period of incident.
lots of active threads within the period of incident.
lots of blocked …
- 523
22
votes
1
answer
27k
views
Meaning of 'locks rec but not gap waiting' in deadlock report
DETECTED DEADLOCK Report
LATEST DETECTED DEADLOCK
------------------------
2015-09-25 15:27:24 1b8084000
*** (1) TRANSACTION:
TRANSACTION 5226928, ACTIVE 0 sec fetching rows
mysql … tables in use 1, locked 1
LOCK WAIT 31 lock struct(s), heap size 6544, 548 row lock(s)
MySQL thread id 71, OS thread handle 0x1b45be000, query id 4085356 localhost root Creating sort index …
- 523
0
votes
0
answers
1k
views
InnoDB locking: what does index record mean?
From MySQL documentation
Record Locks
A record lock is a lock on an index record.
what does index record mean for cluster index?
what does index record mean for secondary index? … Is it a data struct in MySQL source code?
Reference
This article seems useful, but I just don't understand. …
- 523
1
vote
MySQL: How to decrease sleep process's time out?
MySQL process has completed the execution of query, but the client(Rails) doesn't exit.
Why does it happen? … Mysql show processlist lists many processes sleep and info = null? …
- 523
0
votes
0
answers
20
views
InnoDB: does `redo log` contain initial value and final value? or just final value?
start transaction;
update users set age = 34 where user_id = 3 // update age from 30 to 34 years old.
....
....
when I am updating the age of this user, InnDB will write redo log.
What's the stru …
- 523
1
vote
3
answers
683
views
InnoDB: will uncommitted transaction produce redo log?
Before MySQL commit a transaction, it will write REDO log first, then commit the transaction, that is write ahead log. …
- 523
1
vote
Accepted
InnoDB: will uncommitted transaction produce redo log?
Based on Jeremy Cole's presentation InnoDB: A journey to the core III in Percona Live MySQL Conference 2015. … Reference
https://www.percona.com/live/mysql-conference-2015
https://docplayer.net/62963586-Innodb-a-journey-to-the-core-ii-jeremy-cole-and-davi-arnaut.html …
- 523
1
vote
1
answer
2k
views
How does lock works when delete rows through secondary index in InnoDB?
Post", 28);
Lock wait timeout exceeded; try restarting transaction
session2>insert into follows(followable_type, followable_id) value ("Post", 32);
Query OK, 1 row affected (0.01 sec)
Test Result
MySQL … So I really confused by conflict between test result and MySQL manual:
How to explain the conflict?
Could you explain the meaning of DELETE FROM ... …
- 523
1
vote
0
answers
599
views
MySQL: why undo log is required in the processes of database recovery?
Record of page modification are written to redo log, and this page is marked as dirty.
then, an incident happen, MySQL crashes! … we restart MySQL, then recover from an incident, there are three steps:
Analysis
Redo, which will restore the state when MySQL crashed.
Undo. …
- 523