The first day of the first MySQL Connect conference is done.  It's been a busy day!  Many attendees are interested in the new MySQL Server 5.6 release, but of course MySQL Cluster is the main draw here.  After a session from Oracle on the new features in 7.2, and early access features in 7.3, I attended Santo Leto's MySQL Cluster 'hands on lab'.  Despite having started more clusters than most, it felt like a new and exciting experience installing and running my cluster alongside everyone else.  The lab machines had some networking issues, but with Santo's help we seamlessly failed-over to some downloads he'd prepared earlier - very professional!

Afterwards it was my turn to talk on the subject of MySQL Cluster performance.  The quality of the questions was impressive - there seems to be a very capable crowd in San Francisco this …

As always, I am a little late, but I want to jump on the bandwagon and mention the recent MySQL Cluster milestone of passing 1 billion queries per minute. Apart from echoing the arbitrarily large ransom demand of Dr Evil, what does this mean?

Obviously 1 billion is only of interest to us humans as we generally happen to have 10 fingers, and seem to name multiples in steps of 10^3 for some reason. Each processor involved in this benchmark is clocked at several billion cycles per second, so a single billion is not so vast or fast.

Measuring over a minute also feels unnatural for a computer performance benchmark - we are used to lots of things happening every second! A minute is a long time in silicon.

What's more, these …

In my last post I described the motivation for the new NDB$EPOCH conflict detection function in MySQL Cluster. This function detects when a row has been concurrently updated on two asynchronously replicating MySQL Cluster databases, and takes steps to keep the databases in alignment.

With NDB$EPOCH, conflicts are detected and handled on a row granularity, as opposed to column granularity, as this is the granularity of the epoch metadata used to detect conflicts. Dealing with conflicts on a …

tl;dr : New 'automatic' optimistic conflict detection functions available giving the best of both optimistic and pessimistic replication on the same data
MySQL replication supports a number of topologies, and one of the most interesting is an active-active, or master-master topology, where two or more Servers accept read and write traffic, with asynchronous replication between them.

This topology has a number of attractions, including :

• Potentially higher availability
• Potentially low impact on read/write latency
• Service availability insensitive to replication failures
• Conceptually simple

…

The HandlerSocket project is described in Yoshinori Matsunobu's blog entry under the title 'Using MySQL as a NoSQL - A story for exceeding 750,000 qps on a commodity server'. It's a great headline and has generated a lot of buzz. Quite a few early commentators were a little confused about what it was - a new NoSQL system using InnoDB? A cache? In memory only? Where does Memcached come in? Does it support the Memcached protocol? If not, why not? Why is it called HandlerSocket?

Inspirations from Memcache may include the focus on simplicity, performance and a simple human readable protocol. As Yoshinori says, Kazuho Oku has already implemented a MySQLD-embedded Memcached server, no need to do it again. What's more, the Memcache protocol …

Unlike most other MySQL storage engines, Ndb does not perform all of its work in the MySQLD process. The Ndb table handler maps Storage Engine Api calls onto NdbApi calls, which eventually result in communication with data nodes. In terms of layers, we have SQL -> Handler Api -> NdbApi -> Communication. At each of these layer boundaries, the mapping between operations at the upper layer to operations at the lower layer is non trivial, based on runtime state, statistics, optimisations etc.

The MySQL status variables can be used to understand the behaviour of the MySQL Server in terms of user commands processed, and also how these map to some of the Storage Engine Handler Api calls.

Status variables tracking user commands start with …

When MySQL AB bought Sun Microsystems in 2008 (or did Sun buy MySQL?), most of the MySQL team merged with the existing Database Technology Group (DBTG) within Sun. The DBTG group had been busy working on JavaDB, Postgres and other DB related projects as well as 'High Availability DB' (HADB), which was Sun's name for the database formerly known as Clustra.

Clustra originated as a University research project which spun out into a startup company and was then acquired by Sun around the era of dot-com. A number of technical papers describing aspects of Clustra's design and history can be found online, and it is in many ways similar to Ndb Cluster, not just in their shared Scandinavian roots. Both are shared-nothing parallel databases originally aimed at the Telecoms market, supporting high availability and horizontal scalability. Clustra has an impressive feature set and …