Few weeks ago with a big curiosity I was reading several articles published by Percona about TPCC Benchmark results and MySQL 8.0 "checkpointing" issues..

Unfortunately, in these articles there was no any explanation nor any tentative to understand what is going on, an probably at least try and validate some "first coming in mind" tuning / troubleshooting options.. (And even no any try to show in action so often advertised PMM, and see on what it'll point ?)..

All in all, in the following article I'll try to feel up the "white holes" left in this TPCC testing..

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Disclaimer: the following script only works for Percona Server for MySQL 5.7, and relies on enabling performance schema (PS) instrumentation which can add overhead on high concurrent systems, and is not intended for continuous production usage as it’s a POC (proof of concept).

Introduction

In Percona Support, we frequently receive tickets related to deadlocks and even though the deadlock concept is simple, troubleshooting might not be in all cases. 

As explained in How to Deal with MySQL Deadlocks, a deadlock occurs when two or more transactions mutually hold and request for locks, creating a cycle of dependencies. MySQL will detect deadlocks and kill one of the transactions (making it rollback), and the deadlock will be printed in SEIS (show engine innodb status). Limitations of using this approach …

In Percona Kubernetes Operator for Percona XtraDB Cluster (PXC) versions prior to 1.5.0, there were two methods for upgrading PXC clusters, and both of these use built-in StatefulSet update strategies. The first one is manual (OnDelete update strategy) and the second one is semi-automatic (RollingUpdate strategy). Since the Kubernetes operator is about automating the database management, and there are use cases to always keep the database up to date, a new smart update strategy was implemented.

Smart Update Strategy

The smart update strategy can be used to enable automatic context-aware upgrades of PXC clusters between minor versions. One of the use cases for automatic upgrades is if you want to get security …

If you plan for example to have a bastion host in the cloud to access all your MySQL servers and use only MySQL Shell, the first time you connect to one of the host, you will realize that MySQL Shell prompts for a password but doesn’t ask you to store it of not.

Example:

mysqlsh fred@192.168.5.94
Please provide the password for 'fred@192.168.5.94': ****
MySQL Shell 8.0.21
Copyright (c) 2016, 2020, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its affiliates.
Other names may be trademarks of their respective owners.
Type '\help' or '\?' for help; '\quit' to exit.
Creating a session to 'fred@192.168.5.94'
Fetching schema names for autocompletion… Press ^C to stop.
Your MySQL connection id is 16 (X protocol)
Server version: 8.0.21 MySQL Community Server - GPL
No default schema selected; type \use to set one.
MySQL 192.168.5.94:33060+ ssl JS >
Bye!

As you could see, no …

Rewriting a MySQL query for performance is an important process that every DBA should be aware of so they can fix the wrong queries on runtime without code changes on the application end. ProxySQL has great support for rewriting the queries, which Alkin Tezuysal already explored in his excellent blog ProxySQL Query Rewrite Use Case.

So far, MySQL community provides two built-in query rewrite plugins to perform this task. Recently they introduced the plugin “ddl_rewriter”.

• query rewriter plugin : It has support for INSERT / UPDATE / DELETE / REPLACE statements from MySQL 8.0.12. 
• ddl_rewritter plugin: It supports the CREATE TABLE statement. Introduced at MySQL 8.0.16.

In this blog, I am going to explain the complete process of the implementation and the …

At the Percona engineering team, we often receive requests to analyze changes in MySQL/Percona Server for MySQL behavior from one version to another, either due to regression or a bug fix (when having to point out to a customer that commit X has fixed their issue and upgrading to a version including that fix will solve their problem).

In this blog post, we will analyze the approach used to fix PS-7019 – Correct query results for LEFT JOIN with GROUP BY.

Each release comes with a lot of changes. For example, the difference between MySQL 8.0.19 to 8.0.20:

git diff mysql-8.0.19..mysql-8.0.20 | wc -l
737454
git diff mysql-8.0.19..mysql-8.0.20 --name-only | wc -l
4495

737K lines in 4495 files have changed from one minor version to another.

git …

MySQL Shell 8.0.21 comes with two utilities which can be used to perform logical dumps of all the schemas from an instance (util.dumpInstance()) or selected schemas (util.dumpSchemas()). These tools offer major performance improvements over the mysqldump utility, some of our benchmarks show a throughput up to 3GB/s!…

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Recently I had the opportunity to test a storage device from ScaleFlux called CSD 2000. In this blog post, I will share the results of using it to run MySQL in comparison with an Intel device that had a similar capacity.

First of all, why do we need another storage device? Why is ScaleFlux any different?

The answer is simple; it gives us built-in compression and atomic writes. For many workloads, but especially for database-type workloads, these are very important features.

Because of built-in compression, we can store more data on the ScaleFlux device than on a similar device with the same capacity.

Because of atomic writes, we can disable InnoDB Double Write buffer which means less writes/fsync on the disk layer. This should give us a performance advantage against non-atomic drives.

I ran many different tests on different data sizes, with different …

Undo Tablespaces can be truncated either implicitly or explicitly in MySQL 8.0. Both methods use the same mechanism. This mechanism could cause periodic stalls on very busy systems while an undo tablespace truncate completes. This problem has been fixed in MySQL 8.0.21.…

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So you have waited two weeks (cause the crash isn’t easily repeatable) and finally you get the crash again. You check your non-datadir core file directory with loads of free space and discover nothing was written. When MySQL crashes, you … Continue reading →