April 18, 2014

Measuring Max Replication Throughput on Percona XtraDB Cluster with wsrep_desync

Checking throughput with async MySQL replication Replication throughput is the measure of just how fast the slaves can apply replication (at least by my definition).  In MySQL async replication this is important to know because the single-threaded apply nature of async replication can be a write performance bottleneck.  In a production system, we can tell […]

Schema changes – what’s new in MySQL 5.6?

Among many of the improvements you can enjoy in MySQL 5.6, there is one that addresses a huge operational problem that most DBAs and System Administrators encounter in their life: schema changes. While it is usually not a problem for small tables or those in early stages of product life cycle, schema changes become a […]

How number of columns affects performance ?

It is pretty understood the tables which have long rows tend to be slower than tables with short rows. I was interested to check if the row length is the only thing what matters or if number of columns we have to work with also have an important role. I was interested in peak row […]

Talking MySQL to Sphinx

In the recently released Sphinx version 0.9.9-rc2 there is a support for MySQL wire protocol and SphinxQL – SQL-like language to query Sphinx indexes. This support is currently in its early preview stage but it is still fun to play with. A thing to mention – unlike MySQL Storage Engines, some of which as InfoBright […]

Recovering Innodb table Corruption

Assume you’re running MySQL with Innodb tables and you’ve got crappy hardware, driver bug, kernel bug, unlucky power failure or some rare MySQL bug and some pages in Innodb tablespace got corrupted. In such cases Innodb will typically print something like this: InnoDB: Database page corruption on disk or a failed InnoDB: file read of […]

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 […]

Innodb redo log archiving

Percona Server 5.6.11-60.3 introduces a new “log archiving” feature. Percona XtraBackup 2.1.5 supports “apply archived logs.” What does it mean and how it can be used? Percona products propose three kinds of incremental backups. The first is full scan of data files and comparison the data with backup data to find some delta. This approach […]

Creating GEO-enabled applications with MySQL 5.6

In my previous post I’ve showed some new MySQL 5.6 features which can be very helpful when creating geo-enabled applications. In this post I will show how we can obtain open-source GIS data, convert it to MySQL and use it in our GEO-enabled applications. I will also present at the upcoming Percona Live conference on this […]

Q&A: Common (but deadly) MySQL Development Mistakes

On Wednesday I gave a presentation on “How to Avoid Common (but Deadly) MySQL Development Mistakes” for Percona MySQL Webinars. If you missed it, you can still register to view the recording and my slides. Thanks to everyone who attended, and especially to folks who asked the great questions. I answered as many as we had time […]

How rows_sent can be more than rows_examined?

When looking at queries that are candidates for optimization I often recommend that people look at rows_sent and rows_examined values as available in the slow query log (as well as some other places). If rows_examined is by far larger than rows_sent, say 100 larger, then the query is a great candidate for optimization. Optimization could […]