If you have been around MySQL for any length of time, you are probably aware that choosing the correct data types and optimizing your schema are actually important tasks.  A few years back at Percona Live 2016, I gave an introductory talk on schema review and optimization. Here’s the video:

I was thinking about that talk in the context of some of my current clients.  Though I had worked on extremely large database deployments during my earlier tenure at Percona, it was often more of an outlier.  Now, working as a Technical Account Manager with our largest clients, it is much more common.

The Fundamental Problem

I’d like to expand my thoughts on the “choosing the smallest data type you can” principle from my 2016 slides through the lens of a few of my 2019 …

Percona is happy to announce the release of Percona XtraDB Cluster 5.7.27-31.39 on September 18, 2019. Binaries are available from the downloads section or from our software repositories.

Percona XtraDB Cluster 5.7.27-31.39 is now the current release, based on the following:

• Percona Server for MySQL 5.7.27-30
• Codership WSREP API release 5.7.27
• Codership Galera library 3.28

All Percona software is open-source and free.

Bugs Fixed

• PXC-2432: PXC was not …

Percona is glad to announce the release of Percona XtraDB Cluster 5.6.45-28.36 on September 17, 2019. Binaries are available from the downloads section or from our software repositories.

Percona XtraDB Cluster 5.6.45-28.36 is now the current release, based on the following:

• Percona Server 5.6.45-86.1
• Codership WSREP API release 5.6.44
• Codership Galera library 3.28

All Percona software is open-source and free.

Bugs Fixed

• PXC-2432: PXC was not updating …

To set correct system variable values is the essential step to get the correct server behavior against the workload.
In MySQL, we have many System variables that can be changed at runtime, and most of them can be set at the session or global level.

To change the value of a system variable at the global level in the past, users needed to have SUPER privileges. Once the system variable value is modified as global, the server will change this behavior for the session, and obviously as global scope.

For instance, one of the most commonly adjusted variables is probably max_connections.

If you have max_connection=100 in your my.cnf or as the default value, and during the day as DBA you notice that it is not enough, it is easy just to add new connections on the fly with the command:

SET GLOBAL …

I was recently faced with a real issue about completely exhausting the disk space on MySQL. This was a serious issue because of the continuous outages of the service, as the customer had to constantly restart the server and wait for the next outage.

What was happening? In this article, I’m going to explain it and propose solutions.

Implicit temporary tables

MySQL needs to create implicit temporary tables for solving some kinds of queries. The queries that require a sorting stage most of the time need to rely on a temporary table. For example, when you use GROUP BY, ORDER BY or DISTINCT.  Such queries are executed in two stages: the first is to gather the data and put them into a temporary table, the second is to execute the sorting on the temporary table.

A temporary table is also needed in case of some UNION statements evaluation, for …

I think it is often confusing to compare upstream MySQL and Percona Server for MySQL, and some helpful information can be found in the introductory notes. But what does that really mean for an ordinary DBA, especially if none of the known big extra features are important in a particular use case?

In this article, I would like to start a series of short blog posts highlighting small, often less known, but potentially useful features, available in Percona Server for MySQL. Let’s start with a relatively new feature.

Limit the disk space used by binary logs problem

Historically, dealing with binary logs and the disk space used by them was quite challenging. The only thing that let you control this is the …

It’s bad practice to provide world-writable access to critical files in Linux, though we’ve seen time and time again that this is done to conveniently share files with other users, applications, or services. But with Xtrabackup, preparing backups could go wrong if the backup configuration has world-writable file permissions.

Say you performed a backup on a MySQL instance configured with data-at-rest encryption using the keyring plugin. On the backup directory, the generated backup-my.cnf contains these instructions to load this plugin that will be used by Xtrabackup while preparing the backup:

backup-my.cnf

[mysqld]
innodb_checksum_algorithm=crc32
innodb_log_checksum_algorithm=strict_crc32
innodb_data_file_path=ibdata1:12M:autoextend
innodb_log_files_in_group=2
innodb_log_file_size=1073741824
innodb_fast_checksum=false
innodb_page_size=16384
innodb_log_block_size=512
innodb_undo_directory=./
innodb_undo_tablespaces=0 …

Percona is glad to announce the release of Percona XtraDB Cluster 5.7.26-31.37 on June 26, 2019. Binaries are available from the downloads section or from our software repositories.

Percona XtraDB Cluster 5.7.26-31.37 is now the current release, based on the following:

• Percona Server for MySQL 5.7.26-29
• Codership WSREP API release 5.7.25
• Codership Galera library 3.26

All Percona software is open-source and free.

Bugs Fixed

• PXC-2480: In some …

Percona is glad to announce the release of Percona XtraDB Cluster 5.6.44-28.34 on June 19, 2019. Binaries are available from the downloads section or from our software repositories.

Percona XtraDB Cluster 5.6.44-28.34 is now the current release, based on the following:

• Percona Server 5.6.44-86.0
• Codership WSREP API release 5.6.43
• Codership Galera library 3.26

All Percona software is open-source and free.

Bugs Fixed

• PXC-2480: In some …

Please join Percona’s Principal Support Engineer Sveta Smirnova as she presents Billion Goods in Few Categories: How Histograms Save a Life?

Watch the Recorded Webinar

We store data with the intention to use it: search, retrieve, group, sort, etc. To perform these actions effectively, MySQL storage engines index data and communicate statistics with the Optimizer when it compiles a query execution plan. This approach works perfectly well unless your data distribution is uneven.

Last year I worked on several tickets where data followed …