September 2, 2014

The power of MySQL’s GROUP_CONCAT

In the very early days of Percona Vadim wrote very nice post about GROUP_CONCAT. But I want to show you a bit more about it. When is GROUP_CONCAT useful? Usually while working with Support customers I recommend it when you have aggregation of many-to-many info. It makes the view simpler and more beautiful and it […]

Faster MySQL failover with SELECT mirroring

One of my favorite MySQL configurations for high availability is master-master replication, which is just like normal master-slave replication except that you can fail over in both directions. Aside from MySQL Cluster, which is more special-purpose, this is probably the best general-purpose way to get fast failover and a bunch of other benefits (non-blocking ALTER […]

Speeding up GROUP BY if you want aproximate results

Doing performance analyzes today I wanted to count how many hits come to the pages which get more than couple of visits per day. We had SQL logs in the database so It was pretty simple query:

Unfortunately this query ran for over half an hour badly overloaded server and I had to kill […]

Using GROUP BY WITH ROLLUP for Reporting Performance Optimization

Quite typical query for reporting applications is to find top X values. If you analyze Web Site logs you would look at most popular web pages or search engine keywords which bring you most of the traffic. If you’re looking at ecommerce reporting you may be interested in best selling product or top sales people. […]

Should MySQL Extend GROUP BY Syntax ?

Jan has a good article about finding the row matching some value in the group: This is one illustration of group by limitations in SQL language which is not offset by any MySQL specific extensions,yet As you can see if you want to get one row from the group which is sorted some way you […]

Wrong GROUP BY makes your queries fragile

This is probably well known issue for everyone having some MySQL experience or experience with any other SQL database. Still I see this problem in many production applications so it is worth to mention it, especially as it is connected to MySQL Performance. No it might not affect MySQL Performance per say but it limits […]

GROUP_CONCAT useful GROUP BY extension

(There is an updated version of this post here) MySQL has useful extention to the GROUP BY operation: function GROUP_CONCAT: GROUP_CONCAT(expr) – This function returns a string result with the concatenated non-NULL values from a group. Where it can be useful?

Percona XtraDB Cluster 5.6.20-25.7 is now available

Percona is glad to announce the new release of Percona XtraDB Cluster 5.6 on September 1st 2014. Binaries are available from downloads area or from our software repositories. Based on Percona Server 5.6.20-68.0 including all the bug fixes in it, Galera Replicator 3.7, and on Codership wsrep API 25.7, Percona XtraDB Cluster 5.6.20-25.7 is now […]

Galera replication – how to recover a PXC cluster

Galera replication for MySQL brings not only the new, great features to our ecosystem, but also introduces completely new maintenance techniques. Are you concerned about adding such new complexity to your MySQL environment? Perhaps that concern is unnecessarily. I am going to present here some simple tips that hopefully will let fresh Galera users prevent […]

5 great new features from Percona Cloud Tools for MySQL

It’s been three months since we announced anything for Percona Cloud Tools, not because we’ve been idle but because we’ve been so busy the time flew by!  Here’s the TL;DR to pique your interest: EXPLAIN queries in real-time through the web app Query Analytics for Performance Schema Dashboards: customizable, shared groups of charts Install and […]