I had a customer recently who needed to reduce their database size on disk quickly without a lot of messy schema redesign and application recoding. They didn’t want to drop any actual data, and their index usage was fairly high, so we decided to look for unused indexes that could be removed. Collecting data It’s [...]
Percona Live MySQL Conference and Expo 2013 – News from the Committee – Tutorial Selection Complete
December 3, 2012 By 1 Comment
As Percona Live London is raging in the UK, I thought it fitting to remind everyone about the next big Percona Live: MySQL Conference and Expo 2013 in Santa Clara, Californa on April 22-25, 2013. You can register NOW for this conference, and the Super Saving Registration deadline ends on December 28th, so be sure to [...]
Understanding Multi-node writing conflict metrics in Percona XtraDB Cluster and Galera
November 20, 2012 By 17 Comments
I have addressed previously how multi-node writing causes unexpected deadlocks in PXC, at least, it is unexpected unless you know how Galera replication works. This is a complicated topic and I personally feel like I’m only just starting to wrap my head around it. The magic of Galera replication The short of it is that Galera [...]
Edge-case behavior of INSERT…ODKU
October 27, 2012 By 6 Comments
A few weeks back, I was working on a customer issue wherein they were observing database performance that dropped through the floor (to the point of an outage) roughly every 4 weeks or so. Nothing special about the environment, the hardware, or the queries; really, the majority of the database was a single table with [...]
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:
1 2 3 4 5 6 | CREATE TABLE `t1` ( `c1` int(11) NOT NULL AUTO_INCREMENT, `c2` varchar(10) NOT NULL, PRIMARY KEY (`c1`) ) ENGINE=InnoDB; INSERT INTO `t1` (`c2`) VALUES ('michael'), ('peter'), ('aamina'); |
We run an accidental UPDATE statement that [...]
Announcing Percona Server 5.1.65-14.0
September 4, 2012 By Leave a Comment
Percona is glad to announce the release of Percona Server 5.1.65-14.0 on September 4th, 2012 (Downloads are available here and from the Percona Software Repositories). Based on MySQL 5.1.65, including all the bug fixes in it, Percona Server 5.1.65-14.0 is now the current stable release in the 5.1 series. All of Percona‘s software is open-source and free, all the details of the release can [...]
When is MIN(DATE) != MIN(DATE) ?
September 4, 2012 By 5 Comments
Inspiration for this post is courtesy of a friend and former colleague of mine, Greg Youngblood, who pinged me last week with an interesting MySQL puzzle. He was running Percona Server 5.5.21 with a table structure that looks something like this:
1 2 3 4 5 6 7 8 9 | CREATE TABLE foo ( id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY, uid INT UNSIGNED NOT NULL, update_time DATETIME NOT NULL, .... INDEX `uid` (uid, update_time), INDEX `bar` (some_other_columns) .... ) ENGINE=InnoDB; |
When he ran this query:
1 | SELECT MIN(update_time) FROM foo WHERE update_time IS NOT NULL AND update_time <> '0000-00-00 00:00:00'; |
The result came back as 2012-06-22 10:28:16. [...]
Percona XtraDB Cluster: Multi-node writing and Unexpected deadlocks
August 17, 2012 By 17 Comments
Percona XtraDB Cluster (PXC) and the technology it uses (Galera) is an exciting alternative to traditional MySQL replication. For those who don’t know, it gives you: Fully Synchronous replication with a write latency increase equivalent to a ping RTT to the furthest node Automatic cluster synchronization, both incremental and full restores The ability to read [...]
Percona XtraDB Cluster: Failure Scenarios with only 2 nodes
July 25, 2012 By 6 Comments
During the design period of a new cluster, it is always advised to have at least 3 nodes (this is the case with PXC but it’s also the same with PRM). But why and what are the risks ? The goal of having more than 2 nodes, in fact an odd number is recommended in [...]
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 [...]
