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MariaDB server is a community developed fork of MySQL server. Started by core members of the original MySQL team, MariaDB actively works with outside developers to deliver the most featureful, stable, and sanely licensed open SQL server in the industry.
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MASTER-MASTER AND USING SET USE Problem: ======= In a master-master set-up, a master can show a wrong 'SHOW SLAVE STATUS' output. Requirements: - master-master - log_slave_updates This is caused when using SET user-variables and then using it to perform writes. From then on the master that performed the insert will have a SHOW SLAVE STATUS that is wrong and it will never get updated until a write happens on the other master. On"Master A" the "exec_master_log_pos" is not getting updated. Analysis: ======== Slave receives a "User_var" event from the master and after applying the event, when "log_slave_updates" option is enabled the slave tries to write this applied event into its own binary log. At the time of writing this event the slave should use the "originating server-id". But in the above case the sever always logs the "user var events" by using its global server-id. Due to this in a "master-master" replication when the event comes back to the originating server the "User_var_event" doesn't get skipped. "User_var_events" are context based events and they always follow with a query event which marks their end of group. Due to the above mentioned problem with "User_var_event" logging the "User_var_event" never gets skipped where as its corresponding "query_event" gets skipped. Hence the "User_var" event always waits for the next "query event" and the "Exec_master_log_position" does not get updated properly. Fix: === `MYSQL_BIN_LOG::write' function is used to write events into binary log. Within this function a new object for "User_var_log_event" is created and this new object is used to write the "User_var" event in the binlog. "User var" event is inherited from "Log_event". This "Log_event" has different overloaded constructors. When a "THD" object is present "Log_event(thd,...)" constructor should be used to initialise the objects and in the absence of a valid "THD" object "Log_event()" minimal constructor should be used. In the above mentioned problem always default minimal constructor was used which is incorrect. This minimal constructor is replaced with "Log_event(thd,...)". |
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MySQL Server 5.1 This is a release of MySQL, a dual-license SQL database server. For the avoidance of doubt, this particular copy of the software is released under the version 2 of the GNU General Public License. MySQL is brought to you by Oracle. Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved. License information can be found in the COPYING file. MySQL FOSS License Exception We want free and open source software applications under certain licenses to be able to use specified GPL-licensed MySQL client libraries despite the fact that not all such FOSS licenses are compatible with version 2 of the GNU General Public License. Therefore there are special exceptions to the terms and conditions of the GPLv2 as applied to these client libraries, which are identified and described in more detail in the FOSS License Exception at <http://www.mysql.com/about/legal/licensing/foss-exception.html>. This distribution may include materials developed by third parties. For license and attribution notices for these materials, please refer to the documentation that accompanies this distribution (see the "Licenses for Third-Party Components" appendix) or view the online documentation at <http://dev.mysql.com/doc/>. GPLv2 Disclaimer For the avoidance of doubt, except that if any license choice other than GPL or LGPL is available it will apply instead, Oracle elects to use only the General Public License version 2 (GPLv2) at this time for any software where a choice of GPL license versions is made available with the language indicating that GPLv2 or any later version may be used, or where a choice of which version of the GPL is applied is otherwise unspecified. For further information about MySQL or additional documentation, see: - The latest information about MySQL: http://www.mysql.com - The current MySQL documentation: http://dev.mysql.com/doc Some Reference Manual sections of special interest: - If you are migrating from an older version of MySQL, please read the "Upgrading from..." section. - To see what MySQL can do, take a look at the features section. - For installation instructions, see the Installing and Upgrading chapter. - For the new features/bugfix history, see the MySQL Change History appendix. You can browse the MySQL Reference Manual online or download it in any of several formats at the URL given earlier in this file. Source distributions include a local copy of the manual in the Docs directory.