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New UUID functions in MySQL 8.0.0

MySQL 8.0.0 introduces three new miscellaneous UUID functions of IS_UUID(), UUID_TO_BIN() and BIN_TO_UUID() joining the UUID() (in 5.0) and UUID_SHORT() (in 5.1) functions. See 8.0.0 Release Notes.

Thanks to the great work and hosting by Marcus Popp anybody can test out the SQL syntax of MySQL 8.0.0 using db4free without installing anything. If you want a minimal install Giuseppe Maxia provides docker minimal images of 5.0+ versions …

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Optimizing VividCortex’s Samples View: Part 2

A few weeks ago, I wrote a blog post explaining how sketch sampling methods can be employed to achieve fast 30-day data visibility for monitoring users. The problem we faced was that with that standard of retention, we’ve frequently seen systems that involve nearly a million query samples in a 30-day window, meaning that special solutions are needed in order to avoid overloading users’ browsers.

The solution we’ve found lies in a hash ordering that's proven to be both surprisingly simple and efficient. In this Part 2 post, I’ll look at why it works so well.

Ordering with a Hash

VividCortex’s query samples are stored in MySQL tables. The simplified schema definition looks like this:

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7 Fresh Bugs in MySQL 8.0

This blog post will look at seven bugs in MySQL 8.0.

Friday afternoon is always ideal for a quick look at the early quality of MySQL 8.0! Last Friday, I did just that.

If you haven’t heard the news yet, MySQL 8.0 DMR is available for download on!

Tools to the ready: pquery2, updated 8.0 compatible scripts in Percona-qa and some advanced regex to wade through the many cores generated by the test run. For those of you who know and use, this should mean a lot!

[09:41:50] [21492] ====== TRIAL …
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Three wishes for a new year

(Almost) another new year by Jewish calendar. What do I wish for the following year?

  1. World peace
  2. Good health to all
  3. Relaxed GTID constraints

I'm still not using GTID, and still see operational issues with working with GTID. As a latest example, our new schema migration solution, gh-ost, allows us to test migrations in production, on replicas. The GTID catch? gh-ost has to write something to the binary log. Thus, it "corrupts" the replica with a bogus GTID entry that will never be met in another server, thus making said replica unsafe to promote. We can work around this, but...

I understand the idea and need for the Executed GTID Set. It will certainly come in handy with multi-writer InnoDB Cluster. However for most use cases GTID poses a burden. The reason is that our topologies are imperfect, and we as humans are imperfect, and operations are …

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View Galera Cluster Best Practices Webinar Replay Part One!

Codership’s Galera Cluster Best Practices Webinar for MySQL DBAs and DevOps Part One is now available to watch here and MySQL 8.0 was born in 2005 (which makes it older than Twitter or Google Chrome) when MySQL 5.0 was in early development. 11 years went by but one thing always remained the same: the 5 in MySQL’s major version number. MySQL versions went from 5.0 to 5.1 to 5.5, 5.6 and recently to 5.7. There was always this 5.something.

While this 5 will stay around for a bit longer, it is not alone anymore.

Now there is a duplicate of the website at

where you can create a database on a newly set up MySQL 8.0 server!

MySQL 8.0 is in very early development, the first Development Milestone Release (MySQL 8.0.0 DMR) has just been released on September, 12. It will take several months until there will be a final release. makes it easy to try new features early. The …

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Two Database Sharding Tools for MySQL

In a previous blog post we discussed several approaches to sharding. The most flexible one, sharding using metadata, is also the most complex one to implement. You need to design the meta-database, and build high availability not only for your application data but also for the metadata. On top of that, you need to design your application so it will be aware of the complex database infrastructure beneath - it has to query metadata first and then it has to be directed to a correct shard to read or write data. You will also have to build tools to manage and maintain the metadata. Migrating data requires caution so it has to be done carefully. You also have to make sure that any operations on the production databases are mirrored in the metadata. For instance, have you taken a slave out of rotation? This should be reflected in the metadata. Have you added a new …

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Using the super_read_only system variable

This blog post will discuss how to use the MySQL super_read_only system variable.

It is well known that replica servers in a master/slave configuration, to avoid breaking replication due to duplicate keys, missing rows or other similar issues, should not receive write queries. It’s a good practice to set


 on slave servers to prevent any (accidental) writes. Servers acting as replicas will NOT be in read-only mode automatically by default.



 has an historical issue: users with the SUPER privilege can override the setting and could still run DML queries. Since Percona Server 5.6.21 and MySQL 5.7.8, however, you can use the


 feature to extend the

read_only …
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If enforcing data retention via DROP PARTITION, better watch your auto_increment counter

One of the main tasks that any DBA has to deal with is certainly data retention. Especially when your developers like to store logging and tracking information inside the database. This is not something that I would recommend (don't try it at home!) but when you're late to the party (read: someone had taken this path before you joined) , then you'll have to live with it.

Data retention in MySQL is usually applied by partitioning the table by RANGE on a selected column, usually containing the row creation timestamp. New partitions are created in advance for the coming days or weeks or months, and a script is used that will run nightly and drop partitions that are older than a set retention.

There are many tools that can be used to automate data retention; I have chosen the excellent pdb-parted, a nice and cozy perl script that you can find in the PalominoDB repository on GitHub (since PalominoDB is no longer in existence, …

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MySQL Group Replication: Extended Technical Documentation

A new Group Replication plugin labs release has came out, a little over a week ago. Exciting news! This shows that the team has been working hard to shape up the plugin so that it meets the required feature set, performance and quality standards to be released as GA.…

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