… and many threads will get stuck on glibc/kernel syscalls, which will in turn result in contention on kernel_mutex (trx_sys->mutex… mutex. See an example of such an issue. Related bugs: BUG#54982, BUG#49169. 2) memory allocation for read-view structure is not a… list scanning (due to the read-only transactions optimization), but it still allocates/frees memory for read view structure and that causes drops…
Post: Memory allocators: MySQL performance improvements in Percona Server 5.5.30-30.2
April 15, 2013 By
Post: SHOW INNODB STATUS walk through
July 17, 2006 By 40 Comments
… sql_calc_found_rows * from b limit 5 Trx read view will not see trx with id >= 0 80157601, sees < 0 80157597 ---TRANSACTION 0 80157599, ACTIVE 5 sec... b limit 5 Trx read view will not see trx with id >= 0 80157598, sees < 0 80157594 If you have small number of connections all connections will be printed…
Post: Innodb Table Locks
July 31, 2012 By 4 Comments
… select count(*) from sbtest,sbtest x Trx read view will not see trx with id >= 12304, sees < 12301 As you can see in this case the query self joins… INNODB STATUS does not know anything about MySQL level locks, so table locked on MySQL level with LOCK TABLES will not show up… level will prevent tables from being accessed and will not show up in SHOW ENGINE INNODB STATUS. It is a good practice not to…
Post: ACTIVE with Locks – Now thats a problem !
June 2, 2011 By 2 Comments
… system you should not see transactions spending more than couple of seconds in ACTIVE state. Especially ACTIVE transactions which do not currently run…, query id 1014425 10.10.10.10 user Trx read view will not see trx with id >= 2 1418401228, sees < 2 1418374947 —TRANSACTION 2 1418401057, ACTIVE 295 sec…
Post: Percona XtraDB Cluster: Multi-node writing and Unexpected deadlocks
August 17, 2012 By 17 Comments
… the rest of the nodes in the cluster to see if they will agree to it. If they do, then the commit… root sleeping show engine innodb status Trx read view will not see trx with id >= 83C, sees < 83C TABLE LOCK table `test`.`autoinc` trx id 83B lock mode IX… application-dependent, but if you’re not sure, I’d say you should assume it will be a problem. What can you…
Post: When does Innodb Start Transaction ?
January 11, 2011 By 9 Comments
… status Trx read view will not see trx with id >= F56AEE, sees < F56AEE If you're running in AUTOCOMMIT=0 mode the same logic will apply – setting this mode will NOT start transaction however reading or…
Post: Innodb undo segment size and transaction isolation
January 12, 2011 By 3 Comments
… running queries will cause problems in this case anyway, even if you set transaction isolation to lowest READ-UNCOMMITTED level Innodb will not purge…, it even can be seen in SHOW INNODB STATUS: Trx read view will not see trx with id >= F58464, sees < F58462 but whatever isolation mode you’re using…
Post: Differences between READ-COMMITTED and REPEATABLE-READ transaction isolation levels
August 28, 2012 By 3 Comments
… Consistent read views In REPEATBLE READ, a ‘read view‘ ( trx_no does not see trx_id >= ABC, sees < ABB ) is created at the start of the transaction, and this read view (… in READ COMMITTED gap locks are never created. Since there is no gap lock, the example SELECT .. FOR UPDATE above will not …
Post: Percona Server 5.1.49-rel12.0
September 15, 2010 By 6 Comments
…, we will have both Stable and Release Candidate releases. Release Candidates will introduce new features not … system variable innodb_flush_log_at_trx_commit. (Yasufumi Kinoshita) innodb_fast_index_creation …be delayed if an old consistent read view exists that could see the rows to be purged. Bug…
Post: Implementing efficient counters with MySQL
July 1, 2007 By 16 Comments
…you end up reducing number of reads from database dramatically but writes …also assume you would like to see semi-realtime update for them … not have the problem, if you have innodb_flush_log_at_trx…not only reduce number of updates, say if popular object viewed 1000 times within an hour you still will…
