My last blog, Percona Utilities That Make Major MySQL Version Upgrades Easier, detailed the tools available from the Percona toolkit that assists us with major MySQL version upgrades. The pt-upgrade tool aids in testing application queries and generates reports on how each question performs on servers running various versions of MySQL.

MySQL Shell Upgrade Checker is a utility that helps in compatibility tests between MySQL 5.7 instances and MySQL 8.0 upgrades, which is part of the mysql-shell-utilities. The util.checkForServerUpgrade() function checks whether the MySQL 5.7 instance is ready for the MySQL 8.0 upgrade and generates a report with warnings, errors, and notices for preparing the current MySQL 5.7 setup for upgrading to MySQL 8.0.

We can run this Upgrade Checker Utility in the current MySQL 5.7 …

With the economy slowing down and inflation raging in many parts of the world, your organization will love you if you find ways to reduce the costs of running their MySQL databases. This is especially true if you run MySQL in the cloud, as it often allows you to see the immediate effect of those savings, which is what this article will focus on.

With so many companies announcing layoffs or hiring freezes, optimizing your costs may free enough budget to keep a few team members on or hire folks your team needs so much. 

1. Optimize your schema and queries

While optimizing schema and queries is only going to do so much to help you to save on MySQL costs in the cloud, it is a great thing to start with. Suboptimal …

The title is not entirely true, but ‘FTWRL on MyDumper is not needed anymore for consistent backups’ was a long title. One more time, I wanted to share a new feature in MyDumper. This is related to an important piece: the locking mechanism that mydumper uses to sync all the threads.

MyDumper was born because, at that time, we didn’t have a tool that could take a consistent logical backup using multiple threads. Syncing all the threads was one of the problems, which has been solved using FLUSH TABLE WITH READ LOCK (FTWRL), til all the threads execute START TRANSACTION WITH CONSISTENT SNAPSHOT (STWCS), then we release the FTWRL and all the threads are in sync. We all know that FTWRL is very expensive and difficult to acquire on some database workloads.

I started to think about alternatives to avoid using FTWRL, and my first thought was, why …

One of the questions I am often asked is in what cases I would prefer MyRocks over InnoDB. We have covered MyRocks in our blog previously:

MyRocks Performance – Percona Database Performance Blog

Saving With MyRocks in The Cloud – Percona Database Performance Blog

But it would be good to refresh some materials.

This time I want to take an interesting (and real) data set, which I also covered previously: the Reddit Comments dataset (see Big Dataset: All Reddit Comments – Analyzing with ClickHouse – Percona Database Performance Blog). The dataset is still available for download from …

In Percona Server for MySQL 8.0.29-21, we added one more patch that helps us to build server code on macOS. To be precise here, we still could do this even before this patch but only partially. Now it is possible to build RocksDB Storage Engine as well.

A word of disclaimer here, at the moment, by macOS we still understand macOS for Intel x86_64 architecture (the most recent ARM versions with Apple M1 / M2 processors are out of the scope of this blog post). Moreover, Percona does not provide …

This blog post will discuss the newest feature available in MySQL 8.0.30: dynamic redo log sizing. After the InnoDB buffer pool size, we can say that having a proper size for the redo logs is crucial for MySQL performance. There are numerous blog posts about how to calculate a good redo log size. One of our classic blog posts is this one from Baron: How to calculate a good InnoDB log file size (That blog post is from 2008 and is still a valid formula to use.)

Now, which problem is this feature trying to solve?

In MySQL, the buffer pool and redo log size are settings that do not change frequently. Usually, these settings are set during database installation; after that, they are forgotten until an issue arises. The problem is that they used to be static, which means that you had to restart MySQL so the changes …

In this blog, I will cover important aspects which you need to test when benchmarking replication setup. MySQL has great tools that could be used to test its performance. They include:

sysbench – https://github.com/akopytov/sysbench

BMK-kit – http://dimitrik.free.fr/blog/posts/mysql-perf-bmk-kit.html

mysqlslap – https://dev.mysql.com/doc/refman/8.0/en/mysqlslap.html

LinkBench – https://github.com/facebookarchive/linkbench

I will not describe how to use them here, as you can find instructions on the provided links or in the Percona blog by browsing tags …

MySQL 8.0 is now over four years old and Oracle released the latest quarterly offering today with MySQL 8.0.30, which comes with lots of bug fixes and some interesting additions.  This is my take on the release notes for those who do not have the time to wade through them, comments in italics are my comments and reflect the views of only me. 

This is an interesting release with a good many bug fixes and I urge those who need fixes to upgrade as soon as they can. For everyone else, the TL;DR is that unless you are on the Oracle Cloud Infrastructure or one of the fixed bugs is causing you problems, then upgrade at your leisure. 

Deprecation and removals

Setting the  replica_parallel_workers system variable to 0 is now deprecated and to use single threading set replica_parallel_workers=1 instead.  …

When we run a SELECT in a replica server and it returns a different result to the one we would have obtained had we queried the source server instead, due to changes in the dataset that have not yet been replicated or synchronized to the replica, we get what is known as a stale read. My colleague Marcelo has blogged about Stale Reads and How to Fix Them before.

The need to avoid stale reads is a constraint that leads people into migrating to Percona XtraDB Cluster (PXC) / Galera Cluster or, more recently, Group Replication. I am focusing on PXC and Galera in this short blog post, which, similar to Group Replication, implements not exactly a synchronous replication model but what is commonly referred to as a …

In this blog, I explain how to recover from a replication failure caused by a corrupted relay log file.

MySQL replica stores data received from its source binary log in the relay log file. This file could be corrupted due to various reasons, mostly hardware failures. If this happens, replication will stop working, and the error log on the replica will have entries similar to:

2022-05-12T12:32:07.282374Z 2 [ERROR] Error in Log_event::read_log_event(): 'Event too small', data_len: 0, event_type: 0
2022-05-12T12:32:07.282386Z 2 [ERROR] Error reading relay log event for channel '': slave SQL thread aborted because of I/O
...
2022-05-12T12:32:07.282396Z 2 [ERROR] Slave SQL for channel '': Relay log read failure: Could not parse relay log event entry. The possible reasons are: the master's binary log is corrupted (you can check this by running 'mysqlbinlog' on the binary log), the slave's relay log is corrupted (you can check this by running …