August 22, 2014

How MySQL ‘queries’ and ‘questions’ are measured

MySQL has status variables “questions” and “queries” which are rather close but also a bit different, making it confusing for many people. The manual describing it might not be very easy to understand:

In a nutshell if you’re not using prepared statements the big difference between those is what “Questions” would count stored procedure calls as […]

Investigating MySQL Replication Latency in Percona XtraDB Cluster

I was curious to check how Percona XtraDB Cluster behaves when it comes to MySQL replication latency — or better yet, call it data propagation latency. It was interesting to see whenever I can get stale data reads from other cluster nodes after write performed to some specific node. To test it I wrote quite a […]

How expensive is USER_STATISTICS?

One of our customers asked me whether it’s safe to enable the so-called USER_STATISTICS features of Percona Server in a heavy-use production server with many tens of thousands of tables. If you’re not familiar with this feature, it creates some new INFORMATION_SCHEMA tables that add counters for activity on users, hosts, tables, indexes, and more. […]

Identifying the load with the help of pt-query-digest and Percona Server

Overview Profiling, analyzing and then fixing queries is likely the most oft-repeated part of a job of a DBA and one that keeps evolving, as new features are added to the application new queries pop up that need to be analyzed and fixed. And there are not too many tools out there that can make […]

Why you should ignore MySQL’s key cache hit ratio

I have not caused a fist fight in a while, so it’s time to take off the gloves. I claim that somewhere around of 99% of advice about tuning MySQL’s key cache hit ratio is wrong, even when you hear it from experts. There are two major problems with the key buffer hit ratio, and […]

The new cool MySQL patch has landed! Check your queries performance!

Microslow patch is used by many DBAs and developers to accurately time their queries and to catch those which run less than a second as they can also be a performance killer for a busy application. Recently I have started the development of an updated version of the patch. The basic idea is the same […]

Announcing Percona Playback 0.5

Percona is glad to announce the release of Percona Playback 0.5 on November 26th, 2012. Downloads are available from our download site and Percona Software Repositories. Percona Playback is a tool for replaying the load of one database server to another. Currently it can read queries from MySQL query-log and tcpdump files and run them […]

Find unused indexes

I wrote one week ago about how to find duplicate indexes. This time we’ll learn how to find unused indexes to continue improving our schema and the overall performance. There are different possibilites and we’ll explore the two most common here. User Statistics from Percona Server and pt-index-usage. User Statistics User Statistics is an improvement […]

Introducing tcprstat, a TCP response time tool

Ignacio Nin and I (mostly Ignacio) have worked together to create tcprstat[1], a new tool that times TCP requests and prints out statistics on them. The output looks somewhat like vmstat or iostat, but we’ve chosen the statistics carefully so you can compute meaningful things about your TCP traffic. What is this good for? In […]

Estimating Replication Capacity

It is easy for MySQL replication to become bottleneck when Master server is not seriously loaded and the more cores and hard drives the get the larger the difference becomes, as long as replication remains single thread process. At the same time it is a lot easier to optimize your system when your replication runs […]