Please join Percona’s Chief Technology Officer, Vadim Tkachenko, as he presents How to Rock with MyRocks on Thursday, January 17th at 10:00 AM PDT (UTC-7) / 1:00 PM EDT (UTC-4).

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MyRocks is a new storage engine from Facebook and is available in Percona Server for MySQL. In what cases will you want to use it? We will check different workloads and when MyRocks is most suitable for you. Also, as for any new engine, it’s important to set it up and tune it properly. So, we will review the most important settings to pay attention to.

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Please join Percona’s MySQL Product Manager, Tyler Duzan as he presents Walkthrough of Percona Server MySQL 8.0 on Wednesday, January 9th at 11:00 AM PDT (UTC-7) / 2:00 PM (UTC-4).

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Our Percona Server for MySQL 8.0 software is the company’s free, enhanced, drop-in replacement for MySQL Community Edition. The software includes all of the great features in MySQL Community Edition 8.0. Additionally, it includes enterprise-class features from Percona made available free and open source. …

Please join Percona’s CEO Peter Zaitsev as he presents MySQL 8 for Developers on Wednesday, December 12th, 2018 at 11:00 AM PST (UTC-7) / 2:00 PM EST (UTC-5).

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There are many great new features in MySQL 8, but how exactly can they help your application? This session takes a practical look at MySQL 8 features. It also details which limitations of previous MySQL versions are overcome by MySQL 8. Lastly, what you can do with MySQL 8 that you could not have done before is discussed.

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Working on a test case with sysbench, I encountered this:

mysql> select * from sbtest1 where id = round(rand()*10000, 0);
+------+--------+-------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------+
| id   | k      | c                                                                                                                       | pad                                                         |
+------+--------+-------------------------------------------------------------------------------------------------------------------------+-------------------------------------------------------------+
|  179 | 499871 | 09833083632-34593445843-98203182724-77632394229-31240034691-22855093589-98577647071-95962909368-34814236148-76937610370 | 62233363025-41327474153-95482195752-11204169522-13131828192 |
| 1606 | 502031 | …

Continuing on the series of blog posts about MySQL High Availability, today we will talk about stale reads and how to overcome this issue.

The Problem

Stale reads is a read operation that fetches an incorrect value from a source that has not synchronized an update operation to the value (source Wiktionary).

A practical scenario is when your application applies INSERT or UPDATE data to your master/writer node, and has to read it immediately after. If this particular read is served from another server in the replication/cluster topology, the data is either not there yet (in case of an INSERT) or it still provides the old value (in case of an UPDATE).

If your application or part of your application …

Percona released a Release Candidate (RC) version of Percona Server for MySQL 8.0, the company’s free, enhanced, drop-in replacement for MySQL Community Edition. Percona Server for MySQL 8.0 includes all the features of MySQL Community Edition 8.0, along with enterprise-class features from Percona that make it ideal for enterprise production environments. The latest release offers increased reliability, performance and security.

Percona Server for MySQL 8.0 General Availability (GA) will be available later this year. You learn how to install the release candidate software here. Please …

Recently we had a customer that had issues with a filled disk on the server hosting their Docker pmm-server environment. They were not able to access the web UI, or even stop the pmm-server container because they had filled the /var/ mount point.

Setting correct expectations

The best way to avoid these kinds of issues in the first place is to plan ahead, and to know exactly with what you are dealing with in terms of disk space requirements. Michael Coburn has written a great blogpost on this matter:

https://www.percona.com/blog/2017/05/04/how-much-disk-space-should-i-allocate-for-percona-monitoring-and-management/

We are now using …

With the exception of the three configuration variables described here, ProxySQL will only parse the configuration files the first time it is started, or if the proxysql.db file is missing for some other reason.

If we want to change any of this data we need to do so via ProxySQL’s admin interface and then save them to disk. That’s fine if ProxySQL is running, but what if it won’t start because of these values?

For example, perhaps we accidentally configured ProxySQL to run on port 3306 and restarted it, but there’s already a production MySQL instance running on this port. ProxySQL won’t start, so we can’t edit the value that way:

2018-10-02 09:18:33 network.cpp:53:listen_on_port(): [ERROR] bind(): Address already in use

We could delete proxysql.db and have it reload the configuration files, but …

The release of MySQL 8.0 has brought a lot of bold implementations that touched on things that have been avoided before, such as added support for common table expressions and window functions. Another example is the change in how AUTO_INCREMENT (autoinc) sequences are persisted, and thus replicated.

This new implementation carries the fix for bug #73563 (Replace result in auto_increment value less or equal than max value in row-based), which we’ve only found about recently. The surprising part is that the use case we were analyzing is a somewhat common one; this must be affecting a good number of people out there.

Understanding the bug

The business logic of the use case is such the UNIQUE column found in a table whose id is managed by an AUTO_INCREMENT sequence needs to be updated, and this is done with a …

Some time ago, a customer had a performance issue with an internal process. He was comparing, finding, and reporting the rows that were different between two tables. This is simple if you use a LEFT JOIN and an 

IS NULL

  comparison over the second table in the WHERE clause, but what if the column could be null? That is why he used UNION, GROUP BY and a HAVING clauses, which resulted in poor performance.

The challenge was to be able to compare each row using a LEFT JOIN over NULL values.

The challenge in more detail

I’m not going to use the customer’s real table. Instead, I will be comparing two sysbench tables with the same structure:

CREATE TABLE `sbtest1` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `k` int(10) unsigned DEFAULT NULL,
  `c` char(120) DEFAULT NULL,
  `pad` char(60) DEFAULT NULL, …