Shinguz's blog

Hello dcz01

I would say, this is probably a bug. I can reproduce it on my system (MySQL 5.7 Master and MariaDB 10.6 Galera Cluster).

On this page we have summarised information about downgrading a MariaDB/MySQL database. We do not cover migrating from MySQL to MariaDB or vice versa. For migrations (sidegrade) please look here: MySQL - MariaDB migration and here: Migration between MySQL/Percona Server and MariaDB.

FromDual is pleased to announce the release of the new version 1.2.2 of the popular FromDual Ops Center focmm, a Graphical User Interface (GUI) for MariaDB, MySQL and compatible databases.

• Ops Center 1.2.2 Release Notes, Release Date: 25 April 2024
• Ops Center 1.2.1 Release Notes, Release Date: 7 Februray 2023
• Ops Center 1.2.0 Release Notes, Release Date: 17 January 2023
• Ops Center 1.1.0 Release Notes, Release Date: 7 May 2021
• Ops Center 1.0.0 Release Notes, Release Date: 7 May 2020
• Ops Center 0.9.3 Release Notes, Release Date: 18 February 2020
• Ops Center 0.9.2 Release Notes, Release Date: 13 August 2019
• Ops Center 0.9.1 Release Notes, Release Date: 7 May 2019
• Ops Center 0.9.0 Release Notes, Release Date: 16 April 2019
• Ops Center 0.3.0 Release Notes, Release Date: 13 January 2016
• Ops Center 0.2.0 Release Notes, Release Date: 29 May 2014
• Ops Center 0.1.0 Release Notes, Release Date: 02 January 2014
• Ops Center 0.0.1 Release Notes, Release Date: 01 January 2014

Table of contents

• Review
• One month later
• Size of the tables
• Process list
• Global variables
• Metadata Lock and InnoDB Transaction Lock
• Global status

Review

After we introduced dbstat for MariaDB (and MySQL) a good 5 weeks ago, we naturally also rolled it out on our systems to test the behaviour in daily use (eat your own dog food).

Due to an application error, our replication stopped for 5 days (over Easter). After the problem was solved, the replication was supposed to catch up, which turned out to be very slow. All the usual tricks (innodb_flush_log_at_trx_commit, sync_binlog, etc.) had already been exhausted. So we tried our hand at parallel replication of the MariaDB server.

Recently I had to test a new MariaDB feature that was developed at our request (MDEV-33782). To test this feature I had to build the MariaDB server myself from source, which I have not done for a long time. So a new challenge, especially with CMake…

Table of contents

• Overview
• Preparations
• Activate MaxScale configuration synchronisation
• Change MaxScale parameters
• Add new slave and make MaxScale known
• Remove old slave and make MaxScale known
• How is the configuration synchronised?
• What happens in the event of a conflict?
• Tests
• Deactivating MaxScale configuration synchronisation again
• Literature/sources

Overview

A feature that I recently discovered while browsing is the MaxScale configuration synchronisation functionality.

Table of contents

• Overview
• Preparation of the shards (MariaDB database instances)
  • Create test data
  • Creating roles and users
  • MaxScale Monitor User
  • MaxScale Admin User
  • Create application role and accounts
  • Proxy protocol
• MaxScale SchemaRouter configuration
• Starting and stopping the MaxScale Load Balancer
• Application tests
  • Simple application tests
  • New command show shards
  • More general test
  • Less simple tests
  • More complex application tests
  • Cross-shard tests
• Operation of a MaxScale sharding system
  • Do-on-all-shards
  • Invalidating the database map cache
  • How to change SchemaRouter variables dynamically?
  • Adding and removing a tenant
  • Moving a tenant
  • Adding or removing a shard
  • Customising the configuration files
  • Maintenance work on the shard
• Observation / monitoring of a MariaDB MaxScale sharding system
• Literature / Sources

Overview

This feature should more or less work with MariaDB MaxScale 6.x.y, 22.08.x, 23.02.x, 23.08.x and 24.02.x. We have tested it with the latest MaxScale version 23.08.05, as we encountered problems with an older version (MXS-5026).

Table of contents

• Functionality of dbstat
• How does dbstat work
• How to install dbstat
• Query dbstat
  • table_size
  • processlist
  • trx_and_lck
  • metadata_lock
  • global_variables
  • global_status
• Testing
• Sources

An idea that I have been thinking about for a long time and have now, thanks to a customer, finally tackled is dbstat for MariaDB/MySQL. The idea is based on sar/sysstat by Sebastien Godard:

• MyEnv 3.0.0 Release Notes, Release Date: 23 March 2026
• MyEnv 2.1.1 Release Notes, Release Date: 12 December 2025
• MyEnv 2.1.0 Release Notes, Release Date: 28 February 2024
• MyEnv 2.0.3 Release Notes, Release Date: 2 July 2021
• MyEnv 2.0.2 Release Notes, Release Date: 17 January 2019
• MyEnv 2.0.1 Release Notes, Release Date: 3 October 2018
• MyEnv 2.0.0 Release Notes, Release Date: 15 March 2018
• MyEnv 1.3.1 Release Notes, Release Date: 3 August 2016
• MyEnv 1.3.0 Release Notes, Release Date: 31 January 2016
• MyEnv 1.2.2 Release Notes, Release Date: 12 October 2015
• MyEnv 1.2.1 Release Notes, Release Date: 27 July 2015
• MyEnv 1.2.0 Release Notes, Release Date: 18 April 2015
• MyEnv 1.1.4 Release Notes, Release Date: 11 February 2015
• MyEnv 1.1.3 Release Notes: Skipped, see v1.1.4, Release Date: 30 January 2015
• MyEnv 1.1.2 Release Notes, Release Date: 23 October 2014
• MyEnv 1.1.1 Release Notes, Release Date: 8 September 2014
• MyEnv 1.1.0 Release Notes, Release Date: 23 August 2014
• MyEnv 1.0.5 Release Notes, Release Date: 13 June 2014
• MyEnv 1.0.4 Release Notes, Release Date: 29 April 2014
• MyEnv 1.0.3 Release Notes, Release Date: 25 April 2014
• MyEnv 1.0.2 Release Notes, Release Date: 11 December 2013
• MyEnv 1.0.1 Release Notes, Release Date: 5 November 2013
• MyEnv 1.0 Release Notes, Release Date: 4 October 2013
• MyEnv 0.4 Release notes: none, Release Date: 30 March 2011
• MyEnv 0.3.6 Release notes: none, Release Date: 23 January 2011
• MyEnv 0.3.5 Release notes: none, Release Date: 22 January 2011
• MyEnv 0.3.4 Release notes: none, Release Date: 21 November 2010
• MyEnv 0.3.3 Release notes: none, Release Date: 21 November 2010
• MyEnv 0.3.2 Release notes: none, Release Date: 14 November 2010
• MyEnv 0.3.1 Release notes: none, Release Date: 14 November 2010
• MyEnv 0.3 Release notes: none, Release Date: 13 November 2010
• MyEnv 0.2.7 Release notes: none, Release Date: 12 August 2010
• MyEnv 0.2.6 Release notes: none, Release Date: 12 August 2010
• MyEnv 0.2.5 Release notes: none, Release Date: 12 August 2010
• MyEnv 0.2.4 Release notes: none, Release Date: 12 August 2010
• MyEnv 0.2.3 Release notes: none, Release Date: 19 January 2010
• MyEnv 0.2.2 Release notes: none, Release Date: 7 January 2010
• MyEnv 0.2.1 Release notes: none, Release Date: 31 December 2009
• MyEnv 0.2 Release notes: none, Release Date: 24 December 2009
• MyEnv 0.1.1 Release notes: none, Release Date: 18 July 2008
• MyEnv 0.1 Release notes: none, Release Date: 18 July 2008

The design of a data warehouse differs from relational design. Data warehouses are often designed according to the concept of the star schema.

FromDual has the pleasure to announce the release of the new version 2.1.0 of its popular Database Performance Monitor for MariaDB and Galera Cluster fpmmm.

Translated by deepl.com

Introduction

Two points in advance:

1. A deadlock is a state in which two different transactions are no longer able to continue working because each transaction holds a lock that the other transaction would need. Because both transactions are now waiting for the other transaction to release their locks, neither transaction will release their respective locks. And that would last forever. To avoid this, the MariaDB instance intervenes and kills the transaction that has done less work. The application then receives a deadlock error message of this type:

Scenario: MariaDB Community Server is release every 3 months. The exact date is not known but it is typically about 2 to 3 weeks after the MySQL/Oracle CPU.

FromDual has the pleasure to announce the release of the new version 1.2.1 of its popular FromDual Ops Center focmm, a Graphical User Interface (GUI) for MariaDB, MySQL and compatible databases.

FromDual has the pleasure to announce the release of the new version 1.2.0 of its popular FromDual Ops Center focmm, a Graphical User Interface (GUI) for MariaDB, MySQL and compatible databases.

Table of Contents

• Systemd Notizen
• InnoDB NUMA interleave with MariaDB
• Checking Galera Cluster SST timeout with Systemd
• Kill MariaDB Galera node under Systemd
• MariaDB Memory locking (--memlock) with Systemd
• Who is restarting my mariadbd?
• Location of Systemd unit files

Systemd Notizen

Systemd paged per default nach less. Das ist ungewohnt und doof, weil es gegen allgemeines Linux-Verhalten verstösst. Abhilfe schafft:

A while ago I read a paper about Optimizer Benchmarks: How Good Are Query Optimizers, Really? by Viktor Leis from Fakultät für Informatik of the Technische Universität München.