… READ COMMITTED). What is a gap lock? A gap lock is a lock on the gap between index records. Thanks to this gap lock, when you run the… locks all index records found by the WHERE clause with an exclusive lock and the gaps between them with a shared gap lock. This lock doesn… a shared gap lock preventing the insertion of data to other sessions. How to troubleshoot gap locks? Is possible to detect those gap locks using SHOW…
Post: Differences between READ-COMMITTED and REPEATABLE-READ transaction isolation levels
August 28, 2012 By 3 Comments
… they are all related to locking. Extra locking (not gap locking) It is important to remember that InnoDB actually locks index entries, not rows. During… row’ problem. In addition, in READ COMMITTED gap locks are never created. Since there is no gap lock, the example SELECT .. FOR UPDATE above…
Post: Innodb performance gotcha w Larger queries.
August 28, 2009 By 7 Comments
… the SQL for each time. if (trx->isolation_level select_lock_type != LOCK_NONE && trx->mysql_query_str) { /* Scan the MySQL query… (success) { /* It is a plain locking SELECT and the isolation level is low: do not lock gaps */ set_also_gap_locks = FALSE; } } The “REPLACE 1000…_thd)) { /* It is a plain locking SELECT and the isolation level is low: do not lock gaps */ set_also_gap_locks = FALSE; } looking up to…
Post: Paul McCullagh answers your questions about PBXT
November 20, 2009 By 2 Comments
… principles have remained. Pure-MVCC does not do any locking. Read locks are not required because each transaction effectively gets its own…, there are currently no plans to implement InnoDB style “gap locking“. Gap locking effectively involves locking rows that do not exist. This, in turn, means…
Comment: InnoDB's gap locks
April 5, 2012 By 15 Comments
… affected index record has been locked but also the gap before and after that record with a shared gap lock preventing the insertion of data to other sessions.” so how to calculate the shared gap lock ? and another question…
Comment: READ-COMMITED vs REPETABLE-READ in tpcc-like load
February 11, 2010 By 6 Comments
… because InnoDB would lock a gap after the delete in repeatable-read. In RC InnoDB almost never uses a gap locking which is a…
Comment: InnoDB's gap locks
May 7, 2012 By 15 Comments
Hi Miguel ， I’ve tried your example “the affect gap locks to SELECT … FOR UPDATE ” on my server ,and my results … mysql tables in use 1, locked 1 LOCK WAIT 2 lock struct(s), heap size 1216, 1 row lock(s) MySQL thread id 31929…) ——- TRX HAS BEEN WAITING 34 SEC FOR THIS LOCK TO BE GRANTED: RECORD LOCKS space id 57 page no 3 n bits…
Comment: Edge-case behavior of INSERT...ODKU
October 28, 2012 By 6 Comments
…’s like there’s no tomorrow due to mysql’s gap locking. The method I use is to insert into these types…’t depend on a previous row value you can skip locking and just overwrite… I hope I am making some kind…
Comment: Differences between READ-COMMITTED and REPEATABLE-READ transaction isolation levels
August 30, 2012 By 3 Comments
As a side note, if binary logging is enabled, READ-COMMITTED only behaves as you describe when using MIXED or RBR. When using SBR, in order to guarantee correct ordering in the binary log, a gap lock is still taken.
Comment: InnoDB's gap locks
April 4, 2012 By 15 Comments
…://insatiabledemand.ideeli.com/post/18850015294/diagnosing-mysql-auto-inc-and-gap-locks
