A common MySQL strategy to perform updates with accumulating functions is to employ user-defined variables, using the UPDATE [...] SET mycol = (@myvar := EXPRESSION(@myvar, mycol)) pattern.

This pattern though doesn’t play well with the optimizer (leading to non-deterministic behavior), so it has been deprecated. This left a sort of void, since the (relatively) sophisticated logic is now harder to reproduce, at least with the same simplicity.

In this article, I’ll have a look at two ways to apply such logic: using, canonically, window functions, and, a bit more creatively, using recursive CTEs.

• Requirements and background
• …

In this post, the third in a series explaining the internals of InnoDB flushing, we’ll focus on tuning. (Others in the series can be seen at InnoDB Flushing in Action for Percona Server for MySQL and Give Love to Your SSDs – Reduce innodb_io_capacity_max!)

Understanding the tuning process is very important since we don’t want to make things worse or burn our SSDs. We proceed with one section per variable or closely-related variables. The variables are also grouped in sections based on the version of MySQL or Percona Server for MySQL where they are valid. A given variable may be present more …

This post was remaining in stand-by for a long time, specially that I was expecting that observed issues will be fixed soon. But time is going, and the problems are remaining. And I'm constantly asked "why, Dimitri, you're suggesting now to use XFS, while in the past you always suggested EXT4 ??" -- hope the following article will clarify you the "why" and maybe motivate you to do your own evaluations to see how well the things are working for you on your own systems under your own workloads..

NOTE : this will also clarify why the new Double Write did not appear in MySQL 8.0 in 2018, as it was planned, but only recently (http://dimitrik.free.fr/blog/posts/mysql-80-perf-new-dblwr.html)

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On a busy server, the binary logs can end up being one of the largest contributors to amount of disk space used. That means higher I/O, larger backups (you are backing up your binary logs, right?), potentially more network traffic when replicas fetch the logs, and so on. In general, binary logs compress well, so it has been a long time wish for a feature that allowed you to compress the logs while MySQL are still using them. Starting from MySQL 8.0.20 that is now possible. I will take a look at the new feature in this post.

Configuration

The binary log compression feature is controlled by two variables, one for enabling the feature and …

In this day and age, large enterprise companies make use of Ansible, Puppet, or Chef to provision MySQL servers, be it replica sets or clusters. This eases the burden of deployment and workflow management.

However, for some smaller companies, the learning curve hampers the immediate adoption of automation software. This is where the MySQL Shell helps, by allowing you to deploy an N-node InnoDB Cluster or ReplicaSet in less than 60 lines of code.

The Requirements

• Percona Server for MySQL version 8.0.17 or later, preferable version 8.0.19, each node started as standalone servers
• Percona MySQL Shell 8.0 or equivalent upstream version
• MySQL root user and password or equivalent user with grant option
• Hostname configured on each node, can be done with …

MySQL NDB Cluster 8.0.20 new features 

This post is about changes in the implementation of NDB Cluster from MySQL NDB Cluster 8.0 through 8.0.20, as compared to earlier release series. We have included only those of MySQL NDB Cluster 8.0.20 new features which are really interesting and can directly influence / make an impact to performance, scalability and reliability:

• MySQL NDB Cluster  development is in parallel with the development of  MySQL Server going forward. What does that mean for MySQL customers globally NDB 8.0 is developed in, built from, and released with the MySQL 8.0 source code tree and numbering scheme for NDB Cluster 8.0 releases follows the scheme for MySQL 8.0 ( starting with version 8.0.13).
• As of NDB 8.0.18, The identifiers can use up to 64 bytes for databases and tables (the 63-byte limit on identifiers is removed ).
• Generated names for foreign keys …

The new MySQL-8.0.20 release is coming with re-designed InnoDB Double Write Buffer (DBLWR), and, indeed, it's one huge historical PITA less.. -- why it was so painful and cost us much blood in the past, I could not better explain than already done it in the following article yet from 2018 about MySQL on IO-bound workloads.. The story is not complete, as it's missing the 2019's chapter (will tell it later, np) -- but if you'll (re)read the mentioned above article first, you'll better understand the next ;-))

But at least the current post is only about good news now -- the new DBLWR and how it helps to solve historical MySQL performance problems ! -- and as one picture is better than million words, I'll try to save 3M words here (as there are 3 pictures in this article ;-))

Well, I'll also skip all new design details …

A couple of weeks ago, one of our customers reached us asking about the WARNING messages in their MySQL error log. After a while, there were a few more requests from some other customers asking whether to worry about these messages or not. In this post, I am going to write about the condition at which this WARNING message is written into the log and will explain some of the fundamentals behind the scene.

Look at the warningmber message which appears in the MySQL error log. It says it’s difficult to find a free block in the buffer pool and searched through the pool in a loop for 336 times. This is something weird to imagine; why would it have to go in a loop so many times? Let’s try to understand this.

[Warning] InnoDB: Difficult to find free blocks in the buffer pool (336 search iterations)! 0 failed attempts to flush a page! Consider increasing the buffer pool size. It is also possible that in your Unix version …

This presentation covers about the basics of Group replication in MySQL 8.0. Group replication world on the basis of Multi Paxos ( a variant of it ). The author covers the leader election algorithm , switching the primary node and replication modes in this presentation.

Group Replication in MySQL 8.0 ( A Walk Through ) from Mydbops

Like to have this high availability MySQL solution configured on your environment. Mydbops Consultants can provide the best solution with right cost for performance.

MySQL has come up with window function in latest GA MySQL 8.0 . It is a major leap in SQL for MySQL. This presentation provides an overview to window function in MySQL 8.0.

Window functions in MySQL 8.0 from Mydbops Window Function in MySQL 8.0