The latest from the MySQL community

Recently I blogged about identifying necessary index changes when changing the character set for a MySQL database. In this follow-up post I want to talk about general schema changes that you should consider when changing your character set from latin1 to utf8, from utf8 to utf8mb4, etc. The main issue is with long VARCHAR columns and columns with columns with length limits that are enforeced in bytes rather than characters.

The manual points out the main areas where you may have trouble:

• A TINYTEXT column can hold up to 255 bytes, so it can hold up to 85 3-byte or 63 4-byte characters. Suppose that you have a TINYTEXT column that uses utf8 but must be able to …

This Log Buffer edition works it way through some of the coolest blog posts from Oracle, SQL Server and MySQL of the past week.

Oracle:

• What if I’m a developer or QA person using a copy of production database to do my work. What if my copy of production is now out of date and I want to refresh my data with the data as it is on production.
• Direct path and buffered reads again.
• Copy Data Management for Oracle Database with EMC AppSync and XtremIO.
• Little things worth knowing: automatic …

On September 21st, we released Percona XtraDB Cluster 5.6.25. This is the first PXC release supporting proxy-protocol that has been included in Percona Server since 5.6.25-73.0.

With this blog post, I want to promote a new feature that you may have ignored.

Let’s start with a description of the use case:

Architecture Overview:

HAProxy is configured like this:

listen 3307-active-passive-writes 0.0.0.0:3307
    mode tcp
    balance …

Join us for this live webinar on Tuesday, October 27th, led by our colleague Art van Scheppingen, Senior Support Engineer at Severalnines. Art recently joined us from Spil Games in Amsterdam, where he was Head of Database Engineering. He’ll be discussing and demonstrating the new release of ClusterControl and will be available for questions on its new features.

Register here for Asia PAC / Europe MEA timezones

Register here for Latin AMER / North AMER timezones

This is our …

Percona is glad to announce the new release of Percona XtraDB Cluster 5.6 on October 15th 2015. Binaries are available from downloads area or from our software repositories.

Based on Percona Server 5.6.26-74.0 including all the bug fixes in it, Galera Replicator 3.12, and on …

Update 2016-01-30: restarting the IO_THREAD might be considered useful in some situations (avoiding MDEV-9138).  Look for "in contrast, if the IO thread was also stopped first" in MDEV-6589 for more information.

In a previous post, I listed some sequences of commands that you should not run on a MariaDB slave that is lagging and which is using the GTID protocol.  Those are the following (do not

A lot of monitoring systems have a goal of end-to-end tracing, from “click to disk” or something similar. This is usually implemented by adding some kind of tracing information to requests. You can take a look at X-Trace or Zipkin for a couple of examples. The idea is that you can collect complete traces of the entire call tree a user request generates, even across services and through different subsystems, so a slow web page load can be blamed on an overutilized disk somewhere.

I was at a database conference recently where this topic came up, and someone mentioned “blaming” resource usage on any of a variety of things. An example was blaming all disk I/O operations on tenants in a multi-tenant SaaS service. (My ears perked up, because VividCortex is such a service.)

VividCortex doesn’t do end-to-end tracing and it’s not a goal for us. However, the conversation made me pause and reexamine how I made the decision to …

A lot of times I’ve found the need to create a “Shop” page that shows the root category as an anchor (with layered navigation, for example). There are also a couple questions floating around on Stackexchange about how to have root categories be shown like normal categories.

By default Magento won’t show the root category for reasons I’ve still not found out.

There are a lot of modules that have that functionality, like Amasty’s Improved Navigation. However, it turns out it’s also pretty easy to do yourself.

In the Mage_Catalog_CategoryController::_initCatagory (yes, it’s spelled wrong) there is the following check:

if (!Mage::helper('catalog/category')->canShow($category)) {
        return false;
}

The canShow method …

Hello! I have posted this entry on the MySQL Server team's blog:
Storing UUID Values in MySQL Tables

After seeing that several blogs discuss storage of UUID values into MySQL, and that this topic is recurrent on forums, I thought I would compile some sensible ideas I have seen, and also add a couple new ones.

Different techniques

Say we have a table of users, and each user has a UUID.…