…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…lock_mode X locks gap before rec If you have lot of gaps locks in…
Post: SELECT LOCK IN SHARE MODE and FOR UPDATE
August 6, 2006 By 51 Comments
Baron wrote 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…) mysql> select * from tst lock in share mode; +—+ | i | +—+ | 1 | +—+ 1 row in set (0.00 sec) mysql> select * from tst for update; +—+ | i | +—+ | 1 | +—+ 1 row in…
Post: How much memory Innodb locks really take ?
July 13, 2006 By 11 Comments
…: mysql> begin; Query OK, 0 rows affected (0.00 sec) mysql> select count(i) from sample lock in share mode; +———-+ | count(i) | +———-+ | 1638400 | +———-+ 1 row in set… affected (0.00 sec) mysql> select count(*) from sample where j like “5%” lock in share mode; +———-+ | count(*) | +———-+ | 102216 | +———-+ 1 row in set (4.44 sec…
Post: INSERT INTO ... SELECT Performance with Innodb tables.
July 12, 2006 By 21 Comments
… perform non locking reads, meaning unless you use some modifiers such as LOCK IN SHARE MODE or FOR UPDATE, SELECT statements will not lock any rows… 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… updating or deleting mysql tables in use 1, locked 1 LOCK WAIT 3 lock struct(s), heap size 320, undo log entries 1 MySQL thread id…
Post: Test Drive of Solid
September 22, 2006 By 5 Comments
… if rows are locked or even modified unless you require locking read, in which case SELECT FOR UPDATE or SELECT … LOCK IN SHARE MODE can be used… for locking reads (SELECT FOR UPDATE/LOCK IN SHARE MODE) as only actual row versions can be locked. With Innodb we would get “SolidDB2″ as result. mysql…
Post: Ultimate MySQL variable and status reference list
January 8, 2011 By 4 Comments
… amazing MySQL manual, especially the option and …commanual local_infileblogpercona.commanual lock_wait_timeoutblogpercona.commanual locked_in_memoryblogpercona.commanual logblogpercona…commanual server_idblogpercona.commanual shared_memoryblogpercona.commanual shared_memory_base_nameblogpercona….
Post: Paul McCullagh answers your questions about PBXT
November 20, 2009 By 2 Comments
… rows are selected in this manner. I should also mention that the consequence of this is that SELECT … LOCK IN SHARE MODE is currently not… work, in other words, hacks. One of the main problems has been running into global locks when calling back into MySQL to do… MySQL calls the engine “init” method on startup it is holding the global LOCK_plugin lock. In init, the engine needs to do recovery. In…
Post: Table locks in SHOW INNODB STATUS
June 8, 2010 By 1 Comment
…MySQL thread id 8, query id 164 localhost root TABLE LOCK table `test/t1` trx id 0 4872 lock mode…locks – Intention exclusive lock does not prevent other threads taking intention shared or even intention exclusive locks…
Comment: SELECT LOCK IN SHARE MODE and FOR UPDATE
April 21, 2008 By 51 Comments
… should actually succeed. Did you test with mysql.exe in two console (dos?) boxes? Using mysql ensures that you operate directly on the server with no other software layers in between. Also… GET_LOCK/RELEASE_LOCK. p.s: did you know that a ‘SELECT id into tmp from mf_banners where id=192 LOCK IN SHARE MODE‘ together…
Comment: INSERT INTO ... SELECT Performance with Innodb tables.
January 1, 2012 By 21 Comments
…josh: No this does not applies in MySQL 5.5+. I’ve already check that on a table … mln rows using insert into select from this table. No lock has been aquired and on the other thread i could… have this exact behaviour you can use mentioned above: “lock in share mode” because this does the lock to be aqquired on the second table
