In this blog post, we’ll look at how replication triggers a Performance Schema issue on Percona XtraDB Cluster.

During an upgrade to Percona XtraDB Cluster 5.6, I faced an issue that I wanted to share. In this environment, we set up three Percona XtraDB Cluster nodes (mostly configured as default), copied from a production server. We configured one of the members of the cluster as the slave of the production server.

During the testing process, we found that a full table scan query was taking four times less in the nodes where replication was not configured. After reviewing mostly everything related to the query, we decided to use perf.

We executed:

perf record -a -g -F99 -p $(pidof mysqld) -- sleep 60

And the query in another terminal a couple of times. …

The event takes place on 3-4 November 2016 at Olympia Conference Centre, London and will provide you with the tools to deliver your most effective data-driven strategy.

We will be exhibiting on stand 514 and we would be delighted
to speak with you over the 2 days.

Come over and speak to us about how your business can benefit from our open source database solutions. We will be offering demos of our products and will show you how your business can benefit from them.

…

The pt-online-schema-change tool has been a workhorse for years, allowing MySQL DBAs to alter tables with minimal impact to application workload, and before MySQL had native online alter capabilities. Although consistently grateful for the tool’s existence, I never liked the messiness of having to use and clean up triggers, and most DBAs have a horror story or two to tell about using any of the online alter methods.

When Github’s online schema transmogrifer (gh-ost; https://github.com/github/gh-ost) was released, then, I jumped on the chance to test it out.

Following are my testing notes. I tried out the flags available to run gh-ost from different locations in a replication setup, both functionally and under load. The load applied was via mysqlslap, using a …

The MySQL developer tools team announces 6.3.8 as our GA release for MySQL Workbench 6.3.

For the full list of changes in this revision, visit
http://dev.mysql.com/doc/relnotes/workbench/en/changes-6-3.html

For discussion, join the MySQL Workbench Forums:
http://forums.mysql.com/index.php?152

Download MySQL Workbench 6.3.8 GA now, for Windows, Mac OS X 10.9+,
Oracle Linux 6 and 7, Fedora 23 and Fedora 24, Ubuntu 16.04
or sources, from:

http://dev.mysql.com/downloads/tools/workbench/

Enjoy!

The MySQL developer tools team announces 6.3.8 as our GA release for MySQL Workbench 6.3.

For the full list of changes in this revision, visit
http://dev.mysql.com/doc/relnotes/workbench/en/changes-6-3.html

For discussion, join the MySQL Workbench Forums:
http://forums.mysql.com/index.php?152

Download MySQL Workbench 6.3.8 GA now, for Windows, Mac OS X 10.9+,
Oracle Linux 6 and 7, Fedora 23 and Fedora 24, Ubuntu 16.04
or sources, from:

http://dev.mysql.com/downloads/tools/workbench/

Enjoy!

Dear MySQL users,

The MySQL developer tools team announces 6.3.8 as our GA release for
MySQL Workbench 6.3.

For the full list of changes in this revision, visit
http://dev.mysql.com/doc/relnotes/workbench/en/changes-6-3.html

For discussion, join the MySQL Workbench Forums:
http://forums.mysql.com/index.php?152

Download MySQL Workbench 6.3.8 GA now, for Windows, Mac OS X 10.9+,
Oracle Linux 6 and 7, Fedora 23 and Fedora 24, Ubuntu 16.04
or sources, from:

http://dev.mysql.com/downloads/tools/workbench/

Percona announces the GA release of Percona Server 5.7.15-9 on October 21, 2016. Download the latest version from the Percona web site or the Percona Software Repositories.

Based on MySQL 5.7.15, including all the bug fixes in it, Percona Server 5.7.15-9 is the current GA release in the Percona Server 5.7 series. Percona’s provides completely open-source and free software. Find release details in the …

This blog post elaborates on the architecture and design of the transactional data dictionary that will be part of MySQL 8.0. Some descriptions of architecture will be implemented in later versions. See  MySQL 8.0 Data Dictionary:  Background and motivation.

The MySQL Data Dictionary Schema The Transactional Data Dictionary in 8.0 has a simplified and uniform handling of dictionary data

Dictionary  tables and system tables store data and meta data needed by the MySQL server.…

MySQL Cluster uses a distributed architecture where we have one primary
replica and one or more backup replicas of all data in the cluster.
In previous versions we have not supported reading from the backup
replicas. The reason for this comes from the transaction algorithm in
the NDB storage engine. When the transaction have committed we have
unlocked the rows in the primary replica, but the locks in the backup
replica is unlocked in the complete phase.

The impact of this is that we could potentially perform an update
of a row and then immediately read it and not see our own write. To
avoid this problem we have avoided to read the backup replica.

If it is important to read the backup replica then we need to ensure
that transactions are not reported back to the user until the complete
phase.

When we decided to support read from …

When your car doesn’t start, you don’t just blindly change the battery, starter, fuel pump, spark plugs or all of the above. Instead, you go to your mechanic and ask him to check what is wrong (or you check it yourself if you are the mechanic) and then fix whatever is broken.

Yet very often I see DBAs doing exactly the opposite with their MySQL servers. Rather than assessing what is the server so busy with, they keep changing configuration options until the problem “goes away”. Alternatively, they add more RAM, more CPUs or faster disks, depending on which resources seems to be the most busy at a time. Or they switch to a new server altogether.

MySQL (with a help of some tools) has a really convenient way to analyse the workload and see clearly what exactly is MySQL so busy doing. And even how much improvement you can expect by, say, fixing a specific MySQL query.

…