April 25, 2014

Handling long-running queries in MySQL with Percona XtraBackup

I recently had a case where replication lag on a slave was caused by a backup script. First reaction was to incriminate the additional pressure on the disks, but it turned out to be more subtle: Percona XtraBackup was not able to execute FLUSH TABLES WITH READ LOCK due to a long-running query, and the […]

Extending Index for Innodb tables can hurt performance in a surprising way

One schema optimization we often do is extending index when there are queries which can use more key part. Typically this is safe operation, unless index length increases dramatically queries which can use index can also use prefix of the new index are they ? It turns there are special cases when this is not […]

Beware of running ANALYZE in Production

As you might know ANALYZE TABLE just quickly updates table statistics using index dives, unlike with MyISAM when it scans indexes holding table lock for long period of time. So ANALYZE TABLE should be very fast and non intrusive operation doing just little update on the data. Right ?

Why MySQL could be slow with large tables ?

If you’ve been reading enough database related forums, mailing lists or blogs you probably heard complains about MySQL being unable to handle more than 1.000.000 (or select any other number) rows by some of the users. On other hand it is well known with customers like Google, Yahoo, LiveJournal,Technocarati MySQL has installations with many billions […]

ScaleArc: Benchmarking with sysbench

ScaleArc recently hired Percona to perform various tests on its database traffic management product. This post is the outcome of the benchmarks carried out by Uday Sawant (ScaleArc) and myself. You can also download the report directly as a PDF here. The goal of these benchmarks is to identify the potential overhead of the ScaleArc […]

Announcing Percona Server 5.5.27-28.0

Percona is glad to announce the release of Percona Server 5.5.27-28.0 on August 23rd, 2012 (Downloads are available here and from the Percona Software Repositories). Based on MySQL 5.5.27, including all the bug fixes in it, Percona Server 5.5.27-28.0 is now the current stable release in the 5.5 series. All of Percona‘s software is open-source and free, all the details of the release can […]

Fishing with dynamite, brought to you by the randgen and dbqp

I tend to speak highly of the random query generator as a testing tool and thought I would share a story that shows how it can really shine. At our recent dev team meeting, we spent approximately 30 minutes of hack time to produce test cases for 3 rather hard to duplicate bugs. Of course, […]

More on dangers of the caches

I wrote couple of weeks ago on dangers of bad cache design. Today I’ve been troubleshooting the production down case which had fair amount of issues related to how cache was used. The deal was as following. The update to the codebase was performed and it caused performance issues, so it was rolled back but […]

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 […]

Upgrading MySQL

Upgrading MySQL Server is a very interesting task as you can approach it with so much different “depth”. For some this is 15 minutes job for others it is many month projects. Why is that ? Performing MySQL upgrade two things should normally worry you. It is Regressions – functionality regressions when what you’ve been […]