…lock and the gaps between them with a shared gap lock. This lock doesn’t only affect to SELECT … FOR UPDATE…locks in your transactions affecting the concurrency and the performance you can disable them in two different…
Post: SELECT LOCK IN SHARE MODE and FOR UPDATE
August 6, 2006 By 51 Comments
… nice article comparing locking hints in MySQL and SQL Server. In MySQL/Innodb LOCK IN SHARE MODE and SELECT FOR UPDATE are more than hints. Behavior will be different from normal SELECT… while SELECT for UPDATE and LOCK IN SHARE MODE sees it. What is happening ? SELECT for UPDATE and LOCK IN SHARE MODE modifiers effectively run in READ-COMMITTED isolation mode even if current isolation mode is REPEATABLE…
Post: INSERT INTO ... SELECT Performance with Innodb tables.
July 12, 2006 By 21 Comments
… in READ-COMMITTED mode, potentially giving different result compared to what pure SELECT would give. This by the way applies to SELECT .. LOCK IN SHARE MODE and SELECT … FOR UPDATE as well. One my ask what is if I’m not using replication and have my binary…
Post: Test Drive of Solid
September 22, 2006 By 5 Comments
…in action, so it seems to work in some cases. However behavior is different from Innodb which will do READ-COMMITED for locking reads (SELECT FOR UPDATE/LOCK IN SHARE MODE…
Post: Paul McCullagh answers your questions about PBXT
November 20, 2009 By 2 Comments
…locks for 2 reasons: to support SELECT FOR UPDATE, and to avoid optimistic locking errors. This makes PBXT’s behavior identical to InnoDB in REPEATABLE READ mode…in this manner. I should also mention that the consequence of this is that SELECT … LOCK IN SHARE MODE…
Post: SHOW INNODB STATUS walk through
July 17, 2006 By 40 Comments
… “OS Waits” for mutexes, as well as for read-write locks. For these information both for exclusive locks and for shared locks is … trx id 0 42313620 lock_mode X locks rec but not gap Record lock, heap no 5 … up with update rate, in this case difference between these values will also grow and innodb…
Post: MySQL Query Cache
July 27, 2006 By 69 Comments
…locked and is being prepared to be updated. So if you’re using query cache in default configuration you can’t assume locking table for…in the query, have extra space or use different case – these would be different queries for…shared…
