The latest from the MySQL community

A long-ago-discussed and much-requested feature, "dynamic compound statements", is working at last.

It's been eleven years since the original discussion of dynamic compound statements for MySQL, as you can see by looking at the worklog task on the wayback machine. (As usual, you have to click the "high level architecture" box to see the meat of the specification.) The essential idea is that one can directly enter compound statements like BEGIN ... END and conditional statements like "IF ... END IF" and looping statements like "WHILE ... END WHILE" without needing a CREATE PROCEDURE or CREATE FUNCTION statement.

The advantages are that one can run conditional or complex sequences of statements without needing an EXECUTE privilege, or affecting the database metadata. This has been a popular feature request, as …

There are a few circumstances where one will not want to run with only MyISAM tables. In this case, it can be beneficial to completely disable InnoDB.

As InnoDB has become more prevalent, disabling it in MySQL requires a little more effort than before.

In MariaDB 10.0, you can still completely disable it as you have done in the past (just add the –skip-innodb option, specify default-storage-engine=MyISAM, and comment out other InnoDB options):

[mysqld]
skip-innodb
default-storage-engine=MyISAM

Alternatively, instead of –skip-innodb, you can instead use “innodb=OFF”:

[mysqld]
skip-innodb
default-storage-engine=MyISAM

In MySQL 5.6, the –skip-innodb option has been deprecated (though still currently works), and since InnoDB is the new “default” storage engine, you must set both “default-storage-engine” and the new “default-tmp-storage-engine” options to “MyISAM”. If you …

I know, what, MyISAM-only? Yes, it’s true, and it occurs more than you might think.

If you do run MyISAM-only, it’s common to have disabled InnoDB altogether (–skip-innodb) to avoid allocating any RAM to it, and to avoid unnecessary files required for backups, and so forth. (See this post if interested in disabling InnoDB in MySQL 5.6 and/or MariaDB 10.0.)

One improvement in MySQL 5.6 and MariaDB 10.0 is the addition of some system tables. The 2 that are in both are `innodb_table_stats` and `innodb_index_stats`, both of which have an engine type of InnoDB. (The 1 additional system table in MariaDB 10.0 is `gtid_slave_pos`, and the 3 additional system tables in MySQL 5.6 are `slave_master_info`, `slave_relay_log_info`, and `slave_worker_info`.)

The issue, with regards to running MyISAM-only, is that these new …

November 7, 2014 By Severalnines

PrestaShop is a popular open source e-commerce software powering over 200,000 online stores, according to the company. We’ve seen a bit of interest into high availability PrestaShop setups, so this post will show you how to achieve that on multiple servers. Note that this setup not only caters for failures, but by load balancing traffic across multiple servers, it also allows the system to scale and handle more users.

This post is similar to our previous posts on web application scalability and high availability:

• Magento - nginx, MySQL Galera Cluster, OCFS2
• Drupal - Apache, MySQL Galera Cluster, csync2 with …

I ran into this the other day, and while the solution is documented in the manual, it was kind of buried, so I thought I’d mention it here (and hopefully make it easier for others searching for this in the future).

In this specific instance, one was running a huge LOAD DATA (10 hours into it) and had to terminate the LOAD DATA command.

Terminating the command is one thing, but preventing InnoDB from trying to undo the rows that were inserted is another.

In this case, the LOAD DATA will easily re-create the table in question, so the existing table can be “thrown out”, so to speak. This, of course, is a *critical* requirement for this operation (i.e., that you can easily re-create the table – either from a load, backup, dump, etc.).

Per the manual:

“If you know that a given table is causing a crash on rollback, you can drop it. You can also use this to stop a runaway rollback caused by a failing …

Facebook recently made opensource, osquery. It gives you operating system data via SQL queries! Its very neat, and you can test this even on MacOSX (it works on that platform & Linux). It is by far the project with the most advanced functionality, linked here in this post.

I noticed that rather quickly, there was a PostgreSQL project, called pgosquery, based on Foreign Data Wrappers with a similar idea. (apparently it was written in less than 15 minutes; so a much lower learning curve than the regular MySQL storage engine interface)

I immediately thought about an older MySQL project, by Chip Turner (then at Google, now at Facebook), called …

October 31, 2014 By Severalnines

When running a MariaDB Cluster or Percona XtraDB Cluster, it is common to use a load balancer to distribute client requests across multiple database nodes. Load balancing SQL requests aims to optimize the usage of the database nodes, maximize throughput, minimize response times and avoid overload of the Galera nodes. 

In this blog post, we’ll take a look at four different open source load balancers, and do a quick benchmark to compare performance:

• HAproxy by HAproxy Technologies
• IPVS by Linux Virtual Server Project
• Galera Load Balancer by Codership
• mysqlproxy by Oracle (alpha)

Note that there are other options out there, e.g. MaxScale from the MariaDB team, that we plan to cover in a future post.

…

Sometimes users ask for something that doesn’t really make sense. On the first glance. But then you start asking and realize that the user was right, you were wrong, and it is, actually, a perfectly logical and valid use case.

I’ve had one of these moments when I’ve heard about a request of making triggers to work on the slave in the row-based replication. Like, really? In RBR all changes made by triggers are replicated from the master to slaves as row events. If triggers would be fired on the slave they would do their changes twice. And anyway, assuming that one only has triggers one the slave (why?) in statement-based replication triggers would run on the slave normally, wouldn’t they?

Well, yes, they would, but one cannot always use statement-based replication. If one could, RBR would’ve never been implemented. There are many cases that statement-based replication cannot handle correctly. Galera requires RBR too. And as …

As of today, Continuent is part of VMware. We are absolutely over the moon about it.

You can read more about the news on the VMware vCloud blog by Ajay Patel, our new boss. There’s also an official post on our Continuent company blog. In a nutshell the Continuent team is joining the VMware Cloud Services Division. We will continue to improve, sell, and support our Tungsten products and work on innovative integration into VMware’s product line.

So why do I feel exhilarated about joining VMware? There are three reasons. 

1.     Continuent is joining a world-class company that is the leader in virtualization and cloud infrastructure solutions. Even …

Percona Live UK is upon us and I have the privilege to present a tutorial on setting up multi-source replication in MariaDB 10.0 on Nov 3, 2014.

If you’re joining me at PLUK14, we will go over setting up two different topologies that incorporates the features in MariaDB. The first is a mirrored topology:

Replication Topologies – Mirrored

This basically makes use of an existing DR environment by setting it up to be able to write to either master. Please be advised, this is normally not recommended due to the complexity of making your application able to resolve conflicts and …