While preparing a post on the design of ZFS based servers for use with MySQL, I stumbled on the topic of fsync call performance. The fsync call is very expensive, but it is essential to databases as it allows for durability (the “D” of the ACID acronym).

Let’s first review the type of disk IO operations executed by InnoDB in MySQL. I’ll assume the default InnoDB variable values.

The first and most obvious type of IO are pages reads and writes from the tablespaces. The pages are most often read one at a time, as 16KB random read operations. Writes to the tablespaces are also typically 16KB random operations, but they are done in batches. After every batch, fsync is called on the tablespace file handle.

To avoid partially written pages in the tablespaces (a source of data corruption), InnoDB performs a doublewrite. During a doublewrite operation, a batch of dirty pages, from 1 to about 100 pages, is …

In this blog post, I’ll look into four ways MySQL executes GROUP BY. 

In my previous blog post, we learned that indexes or other means of finding data might not be the most expensive part of query execution. For example, MySQL GROUP BY could potentially be responsible for 90% or more of the query execution time. 

The main complexity when MySQL executes GROUP BY is computing aggregate functions in a GROUP BY statement. How this works is shown in the documentation for UDF Aggregate Functions. As we see, the requirement is that UDF functions get all values that constitute the single group one …

Join Percona’s Product Manager Michael Coburn as he presents MySQL Troubleshooting and Performance Optimization with Percona Monitoring and Management (PMM) Part 2 on Thursday, January 18, 2018, at 11:00 am PST / 2:00 pm EST (UTC-8).

Register Now

Tags: Percona Monitoring and Management, PMM, Monitoring, MySQL, Performance, Optimization, DBA, SysAdmin, DevOps
Experience Level: Expert

Optimizing MySQL performance and troubleshooting MySQL problems are two of the most critical and challenging tasks for …

Xtrabackup is the most widely open source hot backup tool for MySQL. Xtrabackup support InnoDB and MyISAM engines.It supports both MySQL Server , Percona Server and MariaDB. This presentation covers some of the important features in Xtrabackup.

Pic Courtesy : https://www.flickr.com/photos/robbiewendt/8108744459/

Percona announces the GA release of Percona Server for MySQL 5.7.20-19 on January 3, 2018. Download the latest version from the Percona web site or the Percona Software Repositories. You can also run Docker containers from the images in the Docker Hub repository.

Based on MySQL 5.7.20, including all the bug fixes in it, Percona Server for MySQL 5.7.20-19 is the current GA release in the Percona Server for MySQL 5.7 series. …

Thank you for attending my webinar on Wednesday, December 20, 2017, InnoDB Performance Optimization. In this blog, I will provide answers to the Q & A for the webinar.

Are the T2 CPUs similar to the M4 series?

I would expect them to be similar. Amazon does not disclose what specific version of CPUs they use for T2 instances. More details are available here.

Delay in spinlock code is pretty old code. Need to optimize based on today’s CPU? Your views?

There have been a number of improvements to the InnoDB Spinlock code during the last few years. For example, using CPU wait …

Join Percona’s, CEO and Co-Founder, Peter Zaitsev as he presents InnoDB Performance Optimization on Wednesday, December 20, 2017, at 11:00 am PST / 2:00 pm EST (UTC-8).

InnoDB is one of the most commonly used storage engines for MySQL and Percona Server for MySQL. It balances high reliability with high performance and is the focus of the majority of storage engine development by the MySQL and Percona Server for MySQL teams.

This webinar looks at InnoDB, including new developments in MySQL 5.7 as well as Percona Server for MySQL. In it, Peter explains how to use it, and many of the configuration options that help you to get the best performance from your application.

…

Percona announces the GA release of Percona Server for MySQL 5.7.20-18 on December 14, 2017. Download the latest version from the Percona web site or the Percona Software Repositories. You can also run Docker containers from the images in the Docker Hub repository.

Based on MySQL 5.7.20, including all the bug fixes in it, Percona Server for MySQL 5.7.20-18 is the current GA release in the Percona Server for MySQL 5.7 series. …

Recently there have been several issues reported to me about DDL activity causing MySQL crash scenarios. In one case it stemmed from dropping multiple databases, one after the other in rapid succession. But in the case that I was recently dealing with directly, where we were upgrading to MySQL 5.7, it was the result of mysql_upgrade running an ALTER TABLE FORCE on a 2.2Tb table in order to convert it to the new microsecond precision supporting data format.

The issue occurred after the intermediate table had been completely filled with all the necessary data and right when MySQL would swap out the existing table for the intermediate. After a period of time MySQL crashed and the following InnoDB monitor output was found in the error log.

2017-11-19T00:22:44.070363Z 7 [ERROR] InnoDB: The age of the last checkpoint is 379157140, which exceeds the log group capacity 377483674.
InnoDB: …

In this blog post, I investigate a case of spiking InnoDB Rows inserted in the absence of a write query, and find internal temporary tables to be the culprit.

Recently I was investigating an interesting case for a customer. We could see the regular spikes on a graph depicting “InnoDB rows inserted” metric (jumping from 1K/sec to 6K/sec), however we were not able to correlate those spikes with other activity. The

innodb_row_inserted

 graph (picture from PMM demo) looked similar to this (but on a much larger scale):

Other graphs (Com_*, Handler_*) did not show any spikes like that. I’ve examined the logs (we were not able to enable general log or change the threshold of the slow log), performance_schema, triggers, stored procedures, prepared statements and even reviewed the binary logs. However, I was not able to find any single …