June 19, 2013

Post: Galera Flow Control in Percona XtraDB Cluster for MySQL

May 2, 2013 By 5 Comments

… the receive queue (visible via the wsrep_local_recv_queue global status variable). Donor/Desynced nodes do not apply flow control, though… few settings that are relevant here, and they are all configured via the wsrep_provider_options global variable. gcs.fc_limit This setting controls… tuning flow control in a master/slave cluster might be: mysql> set global wsrep_provider_options=”gcs.fc_limit=500; gcs.fc_master…

Filed Under: Insight for DBAs, Percona Live, XtraDB Cluster Tagged With: , , ,

Post: Is Synchronous Replication right for your app?

May 14, 2013 By 18 Comments

…MySQL replication from this instance, since MySQL replication is asynchronous. What about semi-sync MySQL…, we can (simultaneously) establish global ordering for the … specified by this variable (default is 1 retry)….100 == 0 ) { $db->do( “UPDATE achievements SET count = $last_count where achievement =…

Filed Under: MySQL, Percona Software, XtraDB Cluster Tagged With: , , , , , ,

Post: How to create/restore a slave using GTID replication in MySQL 5.6

February 8, 2013 By 7 Comments

… and set it on the slave. MySQL keeps two global variables with GTID numbers on it: gtid_executed: it contains a representation of the set… server): slave1> reset master; slave1 > show global variables like ‘GTID_EXECUTED’; +—————+——-+ | Variable_name | Value | +—————+——-+ | gtid_executed | | +—————+——-+ slave1 > set global GTID_PURGED=”9a511b7b-7059-11e2-9a24…

Filed Under: MySQL

Post: Can we improve MySQL variable handling ?

February 18, 2012 By 8 Comments

… SESSION variables, yet for some GLOBAL variables setting them back and forth would not be safe. The simple change which would make dealing with MySQL variables in automated way a lot more convenient would be extending INFORMATION_SCHEMA.GLOBAL_VARIABLES Currently as of MySQL 5.5 it contains only variable…

Filed Under: MySQL

Post: Troubleshooting MySQL Memory Usage

March 21, 2012 By 5 Comments

… larger problems with MySQL 5.5 with addition of user variables, stored procedures, prepared …global_temporary_tables where engine=’memory’; +——————————-+ | sum(data_length+index_length) | +——————————-+ | 126984 | +——————————-+ 1 row in set…

Filed Under: Insight for DBAs, MySQL

Post: Helgrinding MySQL with InnoDB for Synchronisation Errors, Fun and Profit

November 24, 2011 By 2 Comments

… not need much introduction, especially to the MySQL server developers. The Valgrind Memcheck tool,… in mutex_get_waiters and mutex_set_waiters. Interestingly, there are comments next…global_system_variables and LOCK_system_variables_hash. Deadlock is possible when one connection issues SHOW VARIABLES…

Filed Under: MySQL

Post: InnoDB Full-text Search in MySQL 5.6 (part 1)

February 26, 2013 By 1 Comment

… of a table that has a FT index for the global variable innodb_ft_aux_table, we should be able to get… work. First, let’s check the stats immediately after setting these variables, and then let’s push some additional data into the…, and see what happens: mysql> set global innodb_ft_aux_table=’test/dir_test_innodb’; mysql> set global innodb_optimize_fulltext_only=1; mysql> select * from information…

Filed Under: Insight for DBAs, Insight for Developers, MySQL Tagged With: , , , , ,

Post: Replication checksums in MySQL 5.6

February 15, 2013 By 3 Comments

…] {msandbox} ((none)) > set global slave_sql…} ((none)) > show global variables like ‘binlog_checksum’; +—————–+——-+ | Variable_name | Value | +—————–+——-+ |…mysql-bin.000001′ at 2793, the last event read from ‘./mysql-bin.000001′ at 2793, the last byte read from ‘./mysql…

Filed Under: MySQL Tagged With: , , ,

Post: 10+ Ways to Crash or Overload MySQL

November 13, 2007 By 20 Comments

… This will not really change until MySQL Server implements Global Resource Management as otherwise you can…say can you create 1000 variables in stored procedure and set 1M result set to each of them ?… variables one can create. Parse Tree The query is internally presented using parse tree inside MySQL…

Filed Under: Insight for DBAs Tagged With:

Post: Infinite Replication Loop

October 10, 2011 By 2 Comments

… normal flow: Replication flow: [1] When you setup MySQL replication, you define the global variable server_id, this value must be unique for… the machines, but the value was not ok in show global variables… it was always 1 !! There was a hidden character in… can try to skip the statements by stopping the slave, set global SQL_SLAVE_SKIP_COUNTER and start the slave again. This…

Filed Under: MySQL
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