… apologies if we weren’t able to get to your question during the initial session, so I’ll address those lingering questions… the MySQL world, except maybe MyISAM files on top of a clustered filesystem with an external lock manager. You might say that MySQL…: ‘./mysql/servers.frm’ ERROR: 1033 Incorrect information in file: ‘./mysql/servers.frm’ Running mysql_install_db under strace, I saw that it was getting…
Post: PHP Sessions - Files vs Database Based
March 27, 2007 By 38 Comments
… or lock tables. So how you can get back your old file based session behavior with MySQL Sessions ? If you have dedicated connection to session database… transactional tables for session you can use GET_LOCK to get same behavior. In the start of the session you can do SELECT GET_LOCK(”,10) and…
Post: InnoDB's gap locks
March 27, 2012 By 15 Comments
… to this gap lock, when you run the same query twice, you get the same result, regardless other session modifications on that table… shared gap lock preventing the insertion of data to other sessions. How to troubleshoot gap locks? Is possible to detect those gap locks using… source of information: http://dev.mysql.com/doc/refman/5.1/en/innodb-locks-set.html. Conclusion MySQL uses REPEATABLE READ as the…
Post: Implications of Metadata Locking Changes in MySQL 5.5
February 1, 2013 By 9 Comments
… metadata locking is that, if you have some really hot tables, for example in web applications its typical to see a “sessions… threads can get piled up waiting for table metadata lock bringing down the MySQL server or causing all the connections to get depleted. There… fails immediately (however due to a different reason): session2 > set session lock_wait_timeout=1;CREATE TABLE t1(i int(11) not…
Post: Troubleshooting MySQL Memory Usage
March 21, 2012 By 5 Comments
… can’t get fancy graph…sessions have created which temporary tables (both in memory and not): mysql> select * from information_schema.global_temporary_tables \G *************************** 1. row *************************** SESSION… 294352 (82672 + 211680) Lock system 318875832 (318747272 + 128560…
Post: How to debug long-running transactions in MySQL
March 8, 2011 By 6 Comments
… use quite a bit. I simply start a screen session and run it in a loop with a 30-…. MB_THRESHOLD=100 # Make sure the disk isn’t getting too full. avail=$(df -m -P /root/tcpdumps/ | awk ‘/^\//{…)”>&2 exit 1 fi host=$(mysql -ss -e ‘SELECT p.HOST FROM information_schema.innodb_lock_waits w INNER JOIN …
Post: Test Drive of Solid
September 22, 2006 By 5 Comments
… id=2; Session 1: mysql> update test2 set names=’solid1′ where id=2; ERROR 1213 (40001): Deadlock found when trying to get lock; try restarting transaction So instead of waiting on row with id=2 to be unlocked by transaction in session 1… would get “SolidDB2″ as result. mysql> update test2 set names=’SolidDB3′ where id=2; ERROR 1213 (40001): Deadlock found when trying to get lock…
Post: Worse than DDOS
August 18, 2008 By 5 Comments
… this all takes another angle. Default file handler means file gets locked while PHP request is being served. In this case because… mysql – waiting on long query to come back) – this is our query if it is waiting on the session file lock we can get… are much easier with say memcached session storage – this does not cause any locks for parallel session use so only the process which…
Post: Timezone and pt-table-checksum
September 25, 2012 By 1 Comment
… From the manual, here is how MySQL handles timezone locality with timestamp fields:…168.1.46,p=…,u=percona lock:1 transaction:1 changing_src:percona…the checksums on the fly to get the actual rows in need of… FOR UPDATE; When you update your session timezone (SET @@session.time_zone = “+01:00″ for …
Post: The new cool MySQL patch has landed! Check your queries performance!
October 31, 2007 By 16 Comments
… same as for its predecessor – to get more information about query execution logged into…statistics. MySQL currently allows you to see many per-session statistics for operations with SHOW SESSION STATUS… localhost [] # Thread_id: 4 # Query_time: 0.503016 Lock_time: 0.000048 Rows_sent: 56 Rows_examined…
