If you are using Galera Cluster in multi-master mode, you will most likely run into transaction conflicts if two clients attempt to modify the same row at the same time. Such conflicts are reported a deadlock errors to the application.

Legacy applications are frequently unable to handle transaction conflicts properly and may not provide sufficient information to debug the source of the problem.

If the wsrep_log_conflicts option is set, Galera can output all the information about transaction conflicts that is available to it to the error log. As it is a dynamic option, you can enable it while the server is running, collect some entries for examination, and disable it to avoid filling up the log.

Decoding the Output

The output from wsrep_log_conflicts may look a bit intimidating at first, but in fact contains a lot of information that can be used to pin-point the offending application, module or SQL operation. The …

DC Energy is a trader in the commodities markets that relies heavily on MySQL. Since trading is time-sensitive, database management and minimal system downtime is a high priority. Prior to deploying VividCortex, DC Energy used query logs and custom tools, scripts and metrics to find and resolve problems. Internal tools did not provide a way to quickly review and assess the enormous amount of data available, and gaining insight into performance was time consuming.

In March 2013, DC Energy began using VividCortex. Joe Kelly, DC Energy associated, highlighted the benefits since installation:

VividCortex has an intuitive interface, and it’s clearly built by a team that understands monitoring because it only shows us what we need to know. It does not overwhelm us with a lot of information we don’t want. Everything I want is accessible, and I am not bogged down by extraneous information.

This has led to faster diagnosis and …

Well it has been awhile since I posted, sorry about that. Today I was watching reruns of the TV show Fringe and when Walter referenced the Fibonacci Sequence I got side tracked with MySQL options for this.

Now this post already existed:

• http://slava-technical.blogspot.com/2010/10/fibonacci-numbers-built-with-sql.html

So I took that post and expanded on it a little, the result is a procedure that you can call and return the range within the Fibonacci Sequence that you are after.

The procedure is below:

delimiter //
CREATE PROCEDURE `Fibonacci`(IN POS INT, IN RANG INT, IN LIMTED INT)
BEGIN
       select FORMAT(Fibonacci,0) AS Fibonacci from (
…

The MariaDB project is pleased to announce the immediate availability of MariaDB Galera Cluster 10.0.20 and MariaDB Galera Cluster 5.5.44. These are Stable (GA) releases.

Download MariaDB Galera Cluster 10.0.20

Release Notes Changelog What is MariaDB Galera Cluster?

Download …

When I joined Pinterest, my first three weeks were spent in Base Camp, where the newest engineering hires work on real production issues across the entire software stack. In Base Camp, we learn how Pinterest is built by building it, and it’s not uncommon to be pushing code and making meaningful contributions within just a few days. At Pinterest, newly hired engineers have the flexibility to choose which team they’ll join, and working on different parts of the code as part of the Base Camp experience can help with this decision. Base Campers typically work on a variety of tasks, but my project was a deep dive into a MySQL performance optimization project.

Pinterest, MySQL and AWS, oh my!

We work with MySQL running entirely inside Amazon Web Services (AWS). Despite using fairly high-powered instance types with RAID-0 SSDs and a fairly simple workload (many point selects by PK or simple ranges) that peaks around 2,000 …

I have created a small program to extract data from an Oracle database in a format suitable for importing into MariaDB (and MySQL I guess). It is pretty fast as it is written in C and uses the OCI interface. Also, it supports most of the Oracle basic types, including BLOB, CLOB and LONG. UTF8 is also supported and there are many generic features, as well as some features specific for later import into MariaDB.

Download the 1.0 version from Sourceforge where the programs source, that is using autotools for building, as well as documentation is available. I have not tested to build on any other version of Oracle than 11, but maybe someone could help me there.

/Karlsson

In the MySQL team, we have been planning for some time to remove the implicit sorting that is provided by GROUP BY. In doing so, we will make a number of existing queries faster (by no longer requiring a sort) as well as unlock opportunities to implement further optimizations.

This is one of the more complicated behaviours to remove, because it is not possible to tell if an application relies upon implicit ordering. Since a GROUP BY query without an ORDER BY clause is a valid query, it is also not reasonable to issue deprecation warnings.

However, one piece of the puzzle that was missing when I last wrote about this problem, is that MySQL 5.7 will …

This Log Buffer Edition gathers a wide sample of blogs and then purifies the best ones from Oracle, SQL Server and MySQL.

Oracle:

• If you take a look at the “alter user” command in the old 9i documentation, you’ll see this: DEFAULT ROLE Clause.
• There’s been an interesting recent discussion on the OTN Database forum regarding “Index blank blocks after a large update that was rolled back.”
• 12c Parallel Execution New Features: 1 SLAVE distribution
• Index Tree Dumps in Oracle 12c …

It was a very long time since I wrote something in this blob, but I have been very busy this spring with MariaDB on Power mostly. This has been a lot of work, but also a lot of fun. So, what is this MariaDB on Power thing all about, well I wrote an introduction to the Power platform late last year. Since then a lot of things has happened though.

One thing is that several service providers out there has adopted Power8 as a platform. To be honest, this really isn't sexy, but it is useful and as a user of one of these services, you will just see the same old Linux you are used to, but potentially it is more powerful and reliable. One such provider is OVH, whose service is more known as RunAbove. If you want to try it, you can do so for free for 7 7 days, just go …

The slides of “Efficient Use of Indexes in MySQL” talk we delivered on SFMySQL Meetup.

This is an introductory talk for developers on MySQL indexes. In my opinion it’s quite important to understand how InnoDB organizes data. If you know how MySQL accesses data it’s easier to write optimal queries.

When working with queries I imagine secondary indexes as a table with records sorted by secondary key fields. This is a powerful concept that helps to understand MySQL logic. It’s also easy to understand complex optimizations like loose index scan.

For example, for index (last_name, rank) the secondary index table looks like:

…