… 4, locked 4 3264 lock struct(s), heap size 440760, 799203 row lock(s) MySQL thread id 38, OS thread handle 0x2b3c1c776940, query id 16838101 localhost root Copying to tmp table create table t as SELECT ld.label_id, cai.inventory_id, COUNT(1) as installed_count from client_app_inventory cai inner join device d on…
Comment: Implications of Metadata Locking Changes in MySQL 5.5
March 27, 2013 By 9 Comments
… SELECT query and not a query that would hold any row lock. The point was to show the implications of a transaction not holding metadata locks on… is waiting on InnoDB row locks by setting innodb_lock_wait_timeout to 1 and then issuing the ALTER: — session 1 start transaction; select * from…
Post: Implications of Metadata Locking Changes in MySQL 5.5
February 1, 2013 By 9 Comments
…query | 0.000002 | | cleaning up | 0.000002 | +———————-+———–+ 17 rows in set (0.00 sec) As you can see that the SELECT query…
Post: Identifying the load with the help of pt-query-digest and Percona Server
December 29, 2011 By 3 Comments
…0 # Query_time: 0.117904 Lock_time: 0.002886 Rows_sent: 1 Rows_examined: 655360 Rows_affected: 0 Rows_read… though is that, if this query would run on a cold MySQL instance, …SELECT wp_options query, this is basically a unique way of identifying the query and simply implies that this is a SELECT query…
Post: SELECT LOCK IN SHARE MODE and FOR UPDATE
August 6, 2006 By 51 Comments
…> commit; Query OK, 0 rows affected (0.01 sec) SESSION2: mysql> select * from tst; Empty set (0.00 sec) mysql> select * from tst lock in… best example would be INSERT INTO MyISAMTable SELECT * FROM INNODBTable; – A lot of shared locks on Innodb table but no updates. Supporting MySQL…
Post: Innodb Table Locks
July 31, 2012 By 4 Comments
… table locking is a bit more complicated than traditional MyISAM table locks. Let me start with some examples. First lets run SELECT Query: —TRANSACTION… the rows in Shared mode. Intention locks are very loose IS lock on the table does not conflict with any other locks other than X lock on…
Post: How much memory Innodb locks really take ?
July 13, 2006 By 11 Comments
… to lock 1638400 rows, making it less than 3 bits per locked row; Now lets see how much exclusinve locks take: mysql> begin; Query OK, 0 rows affected (0.00 sec) mysql> select count(i… – even billion of locked rows should take half GB of memory, which is small fraction of memory used on serious systems. Furtermore you…
Post: INSERT INTO ... SELECT Performance with Innodb tables.
July 12, 2006 By 22 Comments
… transaction to be applied on the slave before INSERT… SELECT statement and possibly result in different data than on master. Locking rows in the source table while reading them protects from this effect as other transaction modifies rows before INSERT … SELECT had… use 1, locked 1 LOCK WAIT 3 lock struct(s), heap size 320, undo log entries 1 MySQL thread id 1794760, query id 6994946…
Post: How FLUSH TABLES WITH READ LOCK works with Innodb Tables
March 23, 2012 By 20 Comments
…SELECT statement to complete in order to complete locking tables. This means if you have workload which includes some very long SELECT queries…
Post: Innodb performance gotcha w Larger queries.
August 28, 2009 By 7 Comments
… on on Innodb level, so I tried running the test with MyISAM tables instead. The process completed in 12 seconds for 1000 rows…. if (trx->isolation_level select_lock_type != LOCK_NONE && trx->mysql_query_str) { /* Scan the MySQL query string; check if SELECT is the first word there…
