April 19, 2014

Generating test data for MySQL tables

One of the common tasks requested by our support customers is to optimize slow queries. We normally ask for the table structure(s), the problematic query and sample data to be able to reproduce the problem and resolve it by modifying the query, table structure, or global/session variables. Sometimes, we are given access to the server […]

InnoDB file formats: Here is one pitfall to avoid

UPDATED: explaining the role of innodb_strict_mode and correcting introduction of innodb_file_format Compressed tables is an example of an InnoDB feature that became available with the Barracuda file format, introduced in the InnoDB plugin. They can bring significant gains in raw performance and scalability: given the data is stored in a compressed format the amount of […]

The use of Iptables ClusterIP target as a load balancer for PXC, PRM, MHA and NDB

Most technologies achieving high-availability for MySQL need a load-balancer to spread the client connections to a valid database host, even the Tungsten special connector can be seen as a sophisticated load-balancer. People often use hardware load balancer or software solution like haproxy. In both cases, in order to avoid having a single point of failure, […]

InnoDB scalability issues due to tables without primary keys

Each day there is probably work done to improve performance of the InnoDB storage engine and remove bottlenecks and scalability issues. Hence there was another one I wanted to highlight: Scalability issues due to tables without primary keys This scalability issue is caused by the usage of tables without primary keys. This issue typically shows […]

utf8 data on latin1 tables: converting to utf8 without downtime or double encoding

Here’s a problem some or most of us have encountered. You have a latin1 table defined like below, and your application is storing utf8 data to the column on a latin1 connection. Obviously, double encoding occurs. Now your development team decided to use utf8 everywhere, but during the process you can only have as little […]

Want to archive tables? Use Percona Toolkit’s pt-archiver

Percona Toolkit’s pt-archiver is one of the best utilities to archive the records from large tables to another tables or files. One interesting thing is that pt-archiver is a read-write tool. It deletes data from the source by default, so after archiving you don’t need to delete it separately. As it is done by default, you […]

MySQL performance: Impact of memory allocators (Part 2)

Last time I wrote about memory allocators and how they can affect MySQL performance in general. This time I would like to explore this topic from a bit different angle: What impact does the number of processor cores have on different memory allocators and what difference we will see in MySQL performance in this scenario? […]

Wow. My 6 year old MySQL Bug is finally fixed in MySQL 5.6

I got the message in the morning today about the bug being fixed in MySQL 5.6.6…. which I reported in Early 2006 (while still being with MySQL) and running MySQL 4.1 I honestly thought this issue was fixed long ago as it was indeed pretty annoying. I must say I’m very impressed with Oracle team […]

Impact of memory allocators on MySQL performance

MySQL server intensively uses dynamic memory allocation so a good choice of memory allocator is quite important for the proper utilization of CPU/RAM resources. Efficient memory allocator should help to improve scalability, increase throughput and keep memory footprint under the control. In this post I’m going to check impact of several memory allocators on the […]

On Character Sets and Disappearing Tables

The MySQL manual tells us that regardless of whether or not we use “SET FOREIGN_KEY_CHECKS=0″ before making schema changes, InnoDB will not allow a column referenced by a foreign key constraint to be modified in such a way that the foreign key will reference a column with a mismatched data type. For instance, if we […]