May 21, 2013

Recovering from a bad UPDATE statement

October 19, 2012 By 5 Comments

Did you just run an UPDATE against your 10 million row users table without a WHERE clause?  Did you know that in MySQL 5.5 that sometimes you can recover from a bad UPDATE statement?  This is possible if you are running in binlog_format=ROW ! Imagine this scenario:

We run an accidental UPDATE statement that [...]

Filed Under: Insight for DBAs, Insight for Developers, MySQL

Logging Deadlock errors

September 19, 2012 By 4 Comments

The principal source of information for InnoDB diagnostics is the output of SHOW ENGINE INNODB STATUS but there are some sections that are not very useful. For example, LATEST DETECTED DEADLOCK only shows, as the name implies, the latest error detected. If you have 100 deadlocks per minute you will be able to see only [...]

Filed Under: Insight for Developers, MySQL

The Math of Automated Failover

September 18, 2012 By 9 Comments

There are number of people recently blogging about MySQL automated failover, based on production incident which GitHub disclosed. Here is my take on it. When we look at systems providing high availability we can identify 2 cases of system breaking down. First is when the system itself has a bug or limitations which does not [...]

Filed Under: Insight for DBAs, MySQL

Write contentions on the query cache

September 5, 2012 By 5 Comments

While doing a performance audit for a customer a few weeks ago, I tried to improve the response time of their top slow query according to pt-query-digest‘s report. This query was run very frequently and had very unstable performance: during the time data was collected, response time varied from 50µs to 1s. When I ran [...]

Filed Under: Insight for DBAs, MySQL

Percona welcomes Drizzle 7.1

April 10, 2012 By Leave a Comment

The Drizzle team has published the first Drizzle 7.1 stable release. The announcement on the Drizzle blog covers some of the major improvements in this release over the previous stable release, Drizzle 7.0. I plan to write a variety of blog posts on each of the new features over the coming weeks. Major features include: Multi [...]

Filed Under: Cloud and NoSQL Tagged With:

Faster Point In Time Recovery with LVM2 Snaphots and Binary Logs

February 23, 2012 By 3 Comments

LVM snapshots is one powerful way of taking a consistent backup of your MySQL databases – but did you know that you can now restore directly from a snapshot (and binary logs for point in time recovery) in case of that ‘Oops’ moment? Let me show you quickly how. This howto assumes that you already [...]

Filed Under: Insight for DBAs

How to convert MySQL’s SHOW PROFILES into a real profile

February 20, 2012 By 12 Comments

SHOW PROFILES shows how much time MySQL spends in various phases of query execution, but it isn’t a full-featured profile. By that, I mean that it doesn’t show similar phases aggregated together, doesn’t sort them by worst-first, and doesn’t show the relative amount of time consumed. I’ll profile the “nicer_but_slower_film_list” included with the Sakila sample [...]

Filed Under: Insight for Developers, MySQL

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

December 29, 2011 By 3 Comments

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 [...]

Filed Under: Insight for DBAs, MySQL

Preprocessing Data

August 8, 2011 By 3 Comments

There are many ways of improving response times for users. There are some people that spend a lot of time, energy and money on trying to have the application respond as fast as possible at the time when the users made the request. Those people may miss out on an opportunity to do some or [...]

Filed Under: Insight for Developers, MySQL

The case for getting rid of duplicate “sets”

May 17, 2011 By 2 Comments

The most useful feature of the relational database is that it allows us to easily process data in sets, which can be much faster than processing it serially. When the relational database was first implemented, write-ahead-logging and other technologies did not exist. This made it difficult to implement the database in a way that matched [...]

Filed Under: MySQL
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