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Presentations at OpenWorld and PerconaLive

During the last month, I presented on MySQL both at Oracle OpenWorld and Percona Live in Amsterdam.  The slides from the presentations have been uploaded to the conference web sites,  and you also find the slides at Slideshare:

MySQL 8.0: Data Dictionary Architecture and Design

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.…

Read any replica in MySQL Cluster 7.5

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

When we decided to support read from …

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Advanced MySQL Slow Query Logging Part 3: fine-tuning the logging process

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.

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MySQL 8.0: Descending Indexes Can Speed Up Your Queries

In this blog, we’ll discuss descending indexes in MySQL 8.0.


The future MySQL 8.0 will (probably) have a great new feature: support for index sort order on disk (i.e., indexes can be physically sorted in descending order). In the MySQL 8.0 Labs release (new optimizer preview), when you create an index you can specify the order “asc” or “desc”, and it will be supported (for B-Tree indexes). That can be especially helpful for queries like “SELECT … ORDER BY event_date DESC, name ASC LIMIT 10″ (ORDER BY clause with ASC and DESC sort).

MySQL 5.6 and 5.7 Index Order

Actually, the support for this syntax ( …

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Fosdem MySQL & Friends Devroom allocation

Hi all,

Fosdem’s organization announced today that our devroom will be hosted in room H. 1308 on Saturday, February 4th.

This room has a capacity of 148 seats, it’s the same room as last year.

Don’t forget to submit your talks !!


Query Classification and Pluggable Parser

Thu, 2016-10-20 10:16

MySQL Connector/C++ 2.0.3 m3 Development Release has been released

MySQL Connector/C++ 2.0.3 is the next development milestone of the MySQL Connector/C++ 2.0 series, and the first public release. Apart from covering more X DevAPI features, it adds a new, plain C API, called XAPI, that offers functionality similar to X DevAPI to applications written in plain C. Thus, not only can MySQL Connector/C++ be used to write C++ applications, as before.

Now, using the XAPI, MySQL Connector/C++ can be used to write plain C applications to access MySQL Database implementing a document store as well as execute traditional plain SQL statements. For more information about XAPI, refer to the documentation at

To learn more about how to write applications using the X DevAPI, see X DevAPI User Guide ( …

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HopsFS based on MySQL Cluster 7.5 delivers a scalable HDFS

The swedish research institute, SICS, have worked hard for a few years on
developing a scalable and a highly available Hadoop implementation using
MySQL Cluster to store the metadata. In particular they have focused on the
Hadoop file system (HDFS) and the YARN. Using features of MySQL
Cluster 7.5 they were able to achieve linear scaling in number of name
nodes as well as in number of NDB data nodes to the number of nodes
available for the experiment (72 machines). Read the press release from
SICS here

The existing metadata layer of HDFS is based on a single Java server
that acts as name node in HDFS. There are implementations to ensure
that this metadata layer have HA by using a backup name node and to
use ZooKeeper for heartbeats and a number of …

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MySQL Cluster 7.5 is GA, best cluster release ever

I have been fairly quiet on my blog for some time. We've been very busy
developing new features for MySQL Cluster 7.5 and ensuring that the
quality is improved even further.

We're now very pleased to release a new version of MySQL Cluster.

MySQL Cluster 7.5 contains a number of new things that makes MySQL
Cluster even better.
1) You can declare a table as a READ_BACKUP table. This means that
the updating transactions will receive the commit acknowledge
a little bit later to ensure that we can always use any of the
replicas for reading. We will use the nearest replica for
committed reads, for locking reads we will still use the primary
replica to avoid deadlocks.

For applications that are mostly read-focused one can make it easier
to set this variable by setting the ndb-read-backup config variable
to 1 in the MySQL Server …

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