Here in Percona Support, we’re receiving several requests per day for help with Percona Cloud Tools installation steps.

So I decided to prepare a step-by-step example of the installation process with some comments based on experience.  Percona Cloud Tools is a hosted service providing access to query performance insights for all MySQL uses. After a brief setup, you’ll unlock new information about your database and how to improve your applications. You can sign up here to request access to the free beta, currently under way.

Some notes

• It’s recommended to do the installation under root.
• If you’re installing pt-agent as root then .pt-agent.conf should be placed in root $HOME
• You could became root …

This is the first in a series of posts highlighting a few of the seldom-used but still handy Percona Toolkit tools.

Have you ever had a problem understanding the EXPLAIN statement output? And are you the type of person who would rather use the command line than a GUI application? Then I would recommend that you use Percona’s pt-visual-explain toolkit. This is one of many Percona Toolkit tools that is useful for those who want to have a different view and an easier time understanding the EXPLAIN output aside from the usual table and vertical views.

As described in the documentation – http://www.percona.com/doc/percona-toolkit/2.2/pt-visual-explain.html#description

“pt-visual-explain reverse-engineers …

When we are hired for a MySQL performance audit, we are expected to review the MySQL configuration and to suggest improvements. Many people are surprised because in most cases, we only suggest to change a few settings even though hundreds of options are available. The goal of this post is to give you a list of some of the most critical settings.

We already made such suggestions in the past here on this blog a few years ago, but things have changed a lot in the MySQL world since then!

Before we start…

Even experienced people can make mistakes that can cause a lot of trouble. So before blindly applying the recommendations of this post, please keep in mind the following items:

• Change one setting at a time! This is the only way to estimate if a change is beneficial.
• Most …

There are many blog posts already written on topics related to “MySQL server memory usage,” but nevertheless there are some who still get confused when troubleshooting issues associated with memory usage for MySQL. As a Percona support engineer, I’m seeing many issues regularly related to heavy server loads – OR OOM killer got invoked and killed MySQL server due to high Memory usage… OR with a question like: “I don’t know why mysql is taking so much memory. How do I find where exactly memory is allocated? please help!”

There are many ways to check memory consumption of MySQL. So, I’m just trying here to explain it by combining all details that I know of in this post.

• Check memory related Global/Session variables.

If you are using …

The other day I was working on an issue where one of the slaves was showing unexpected lag. Interestingly with only the IO thread running the slave was doing significantly more IO as compared to the rate at which the IO thread was fetching the binary log events from the master.

I found this out by polling the SLAVE STATUS and monitoring the value of Read_Master_Log_Pos as it changed over time. Then compared it to the actual IO being done by the server using the pt-diskstats tool from the excellent Percona Toolkit. Note that, when doing this analysis, I had already stopped the slave SQL thread and made sure that there were no dirty InnoDB pages, otherwise my analysis would have …

One of our primary focuses at Percona is performance. Let me make some statements on what is “performance.”

In doing so I will refer to two pieces of content:

• Carry Millsap’s talk “Performance Instrumentation: Beyond What You Do Now” [1]
• White Paper (by Peter and Baron) “Goal-Driven Performance Optimization” [2]

I highly recommend that you familiarize yourself with both of them.

Performance

Performance is about tasks and time.
We say that the system is performing well if it executes a task in an acceptable period of time, or that the …

Sometimes there is a need for keeping large amounts of old, rarely used data without investing too much on expensive storage. Very often such data doesn’t need to be updated anymore, or the intent is to leave it untouched. I sometimes wonder what I should really suggest to our Support customers.

For this purpose, the archive storage engine, added in MySQL 4.1.3, seems perfect as it provides excellent compression and the only DML statement it does allow is INSERT. However, does it really work as you would expect?

First of all, it has some serious limitations. Apart from lack of support for DELETE, REPLACE and UPDATE statements (which may be acceptable for some needs), another one is that it does not allow you to have indexes, although you can have an auto_increment column being either a unique or non-unique index. So usually …

A question often comes when talking about indexing: should we use multiple column indexes or multiple indexes on single columns? Peter Zaitsev wrote about it back in 2008 and the conclusion then was that a multiple column index is most often the best solution. But with all the recent optimizer improvements, is there anything different with MySQL 5.6?

Setup

For this test, we will use these 2 tables (same structure as in Peter’s post):

CREATE TABLE t1000merge (
  id int not null auto_increment primary key,
  i int(11) NOT NULL,
  j int(11) NOT NULL,
  val char(10) NOT NULL,
  KEY i (i),
  KEY j (j)
) ENGINE=InnoDB;
CREATE TABLE t1000idx2 (
  id int not null auto_increment primary key,
  i int(11) NOT NULL,
  j int(11) NOT NULL,
  val char(10) NOT NULL,
  KEY ij (i,j)
) ENGINE=InnoDB;

Tables were …

Table structures are stored in .frm files and in the InnoDB Data Dictionary. Sometimes, usually in data recovery issues, we need to recover those structures to be able to find the lost data or just to recreate the tables.

There are different ways to do it and we’ve already written about it in this blog. For example, we can use the data recovery tools to recover table structures from InnoDB Dictionary or from the .frm files using a MySQL Server. This blog post will be an update of that last one. I will show you how to easily recover the structure from a .frm file and in some cases even …

Recently, one of our support customers faced this: “[ERROR] mysqld: Sort aborted: Server shutdown in progress.” At first it would appear this occurred because of a mysql restart (i.e. the MySQL server restarted and the query got killed during the stopping of mysql). However, while debugging this problem I found no evidence of a MySQL server restart – which proves that what’s “apparent” is not always the case, so this error message was a bit misleading. Check this bug report for further details http://bugs.mysql.com/bug.php?id=18256 (it was reported back in 2006).

I found that there are two possible reasons for this error: Either the MySQL server restarts during execution of the query, or the query got killed forcefully during execution which utilizes the …