July 29, 2014

DBA 101: Sometimes forgotten functionality in the MySQL client

The MySQL client has some functionalities some of us never use. Why would you use them and what is the added value of this? Every DBA and developer has had a moment when he or she needs to connect to a MySQL database using the command line tool. Therefore I’ve written down an explanation of […]

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 […]

MySQL versions shootout

As part of work on “High Performance MySQL, 3rd edition”, Baron asked me to compare different MySQL version in some simple benchmark, but on decent hardware. So why not.

The story of one MySQL Upgrade

I recently worked on upgrading MySQL from one of very early MySQL 5.0 versions to Percona Server 5.1. This was a classical upgrade scenario which can cause surprises. Master and few slaves need to be upgraded. It is a shared database used by tons of applications written by many people over more than 5 years […]

MySQL 4 to MySQL 5 Upgrade performance regressions

This week I already had two serious performance regression cases when upgrading from MySQL 4.0 and 4.1 to MySQL 5.0. By serious I mean several times performance difference not just 5-10% you often see for simple queries due to generally fatter code. The problem in both cases was MySQL 5.0 broken group commit bug. First […]

MySQL Crash Recovery

MySQL is known for its stability but as any other application it has bugs so it may crash sometime. Also operation system may be flawed, hardware has problems or simply power can go down which all mean similar things – MySQL Shutdown is unexpected and there could be various inconsistences. And this is not only […]

MySQL EXPLAIN limits and errors.

Running EXPLAIN for problematic queries is very powerful tool for MySQL Performance optimization. If you’ve been using this tool a lot you probably noticed it is not always provide adequate information. Here is list of things you may wish to watch out. EXPLAIN can be wrong – this does not happen very often but it […]

Binary log file size matters (sometimes)

I used to think one should never look at max_binlog_size, however last year I had a couple of interesting cases which showed that sometimes it may be very important variable to tune properly. I meant to write about it earlier but never really had a chance to do it. I have it now!

Crashes while using MyISAM with multiple key caches

Over last couple of years I have ran into random MySQL crashes in production when multiple key caches were used. Unfortunately this never was frequent or critical enough issue so I could spend time creating repeatable test case and search of the bug in the MySQL database did not find anything. Recently we had this […]