August 27, 2014

Performance gotcha of MySQL memory tables

One performance gotcha with MEMORY tables you might know about comes from the fact it is the only MySQL storage engine which defaults to HASH index type by default, instead of BTREE which makes indexes unusable for prefix matches or range lookups. This is however not performance gotcha I’m going to write about. There is […]

MVCC: Transaction IDs, Log Sequence numbers and Snapshots

MySQL Storage Engines implementing Multi Version Concurrency Control have several internal identifiers related to MVCC. I see a lot of people being confused what they are and why they are needed so I decided to take a time to explain it a bit. This is general explanation, it does not corresponds to Innodb in particular […]

MySQL: Followup on UNION for query optimization, Query profiling

Few days ago I wrote an article about using UNION to implement loose index scan. First I should mention double IN also works same way so you do not have to use the union. So changing query to:

So as you see there are really different types of ranges in MySQL. IN range allows […]

MySQL Query Cache

MySQL has a great feature called “Query Cache” which is quite helpful for MySQL Performance optimization tasks but there are number of things you need to know. First let me clarify what MySQL Query Cache is – I’ve seen number of people being confused, thinking MySQL Query Cache is the same as Oracle Query Cache […]

Choosing proper innodb_log_file_size

If you’re doing significant amount of writes to Innodb tables decent size of innodb_log_file_size is important for MySQL Performance. However setting it too large will increase recovery time, so in case of MySQL crash or power failure it may take long time before MySQL Server is operational again. So how to find the optimal combination […]

When (and how) to move an InnoDB table outside the shared tablespace

In my last post, “A closer look at the MySQL ibdata1 disk space issue and big tables,” I looked at the growing ibdata1 problem under the perspective of having big tables residing inside the so-called shared tablespace. In the particular case that motivated that post, we had a customer running out of disk space in his […]

Notes from the Newb

Notes from the Newb. I’m relatively new to MySQL having come from the world of embedded micro-databases, and though I’m pretty familiar with a number of database systems, I’ve discovered that I have a lot to learn about MySQL. As a new member to the Percona team, I thought I’d have an ongoing blog theme […]

Introducing backup locks in Percona Server

TL;DR version: The backup locks feature introduced in Percona Server 5.6.16-64.0 is a lightweight alternative to FLUSH TABLES WITH READ LOCK and can be used to take both physical and logical backups with less downtime on busy servers. To employ the feature with mysqldump, use mysqldump –lock-for-backup –single-transaction. The next release of Percona XtraBackup will […]

How to fix your PRM cluster when upgrading to RHEL/CentOS 6.4

If you are using Percona Replication Manager (PRM) with RHEL/CentOS prior to 6.4, upgrading your distribution to 6.4 may break your cluster. In this post I will explain you how to fix your cluster in case it breaks after a distribution upgrade that implies an update of pacemaker from 1.1.7 to 1.18. You can also […]

Can’t Create Thread: Errno 11 (A Tale of Two Ulimits)

Recently some of my fellow Perconians and I have noticed a bit of an uptick in customer cases featuring the following error message:

The canonical solution to this issue, if you do a bit of Googling, is to increase the number of processes / threads available to the MySQL user, typically by adding a […]