The latest from the MySQL community

A story around replication lag and Flow-Control.

Overview

In the last few months we had 2 main actors in the the MySQL ecosystem, ProxySQL and Group-Replication (with the evolution to InnoDB Cluster). 

While I had extensively covered the first, my last serious work on GR, goes back to some lab version in the past years. 
Given the decision Oracle made to declare it GA, and the Percona decision to provide some level of support to GR, I decide it was time for me to take a look at it again.
A lot of reviews were already done covering different topics. I saw articles about GR and performance, GR and basic functionalities (or lack of it like automatic node provisioning), GR and ProxySQL and so on.

But one question was coming up over and over in my mind. If GR and InnoDB cluster has to work as alternative to other (virtually) synchronous replication …

In this post, we’ll use a blog poll to find out what operating system you use to run your development database servers.

In our last blog poll, we looked at what OS you use for your production database. Now we would like to see what you use for your development database.

As databases grow to meet more challenges and expanding application demands, they must try and get the maximum amount of performance out of available resources. How they work with an operating system can affect many variables, and help or hinder performance. The operating system you use for your database can impact consumable choices (such as hardware and memory). The operating system you use can also impact your choice of database engine as well (or vice versa).

When new projects, new applications or services or testing new architecture …

In this blog post, I’ll talk about multi-threaded slave statistics printed in MySQL error log file.

MySQL version 5.6 and later allows you to execute replicated events using parallel threads. This feature is called Multi-Threaded Slave (MTS), and to enable it you need to modify the

slave_parallel_workers

 variable to a value greater than 1.

Recently, a few customers asked about the meaning of some new statistics printed in their error log files when they enable MTS. These error messages look similar to the example stated below:

[Note] Multi-threaded slave statistics for channel '': seconds elapsed = 123; events assigned = 57345; worker queues filled over overrun level = 0; waited due a Worker queue full = 0; waited due the total size = 0; waited at clock conflicts = 0 waited (count) …

Group Replication has been around for some time now and the feedback from community is overwhelming. One of the suggestions (BUG#84795) received is related to deploying a mechanism to prevent a server from being updated after stopping group replication.…

This is old news for MySQL/MariaDB expert but people that are starting using InnoDB do not always know that disk space is not automatically released when deleting data from a table.  To explain and demonstrate that, I will take two real-world examples: table1 and table2.

Recently, more than 90% and about 20% of rows were deleted from table1 and table2 (those tables contain real data, I only

Introduction:

• MySQL 5.7 introduces a new feature called virtual/generated column. It is called generated column because the data of this column is computed based on a predefined expression or from other columns.

What is Virtual Column ?

• In general virtual columns appear to be normal table columns, but their values are derived rather than being stored on disk.
• Virtual columns are one of the top features in MySQL 5.7,they can store a value that is derived from one or several other fields in the same table in a new field.

Syntax :

Syntax for adding new virtual column,

==> Alter table table_name add column column_name generated always as column_name virtual;

Example :

Alter table contacts add column generated always as mydbops_test virtual / stored.

GENERATED ALWAYS …

I regularly meet with MySQL customers and I'm still a little surprised to see critical applications running on "not really" recent versions (to put it mildly) :)

The good news is that obviously old versions of MySQL are sufficiently stable and powerful to run the modern business. However, even if I understand that it is sometimes appropriate to freeze all layers of an architecture, it is often a shame not to take advantage of the latest improvements from a performance, stability, security point of view and obviously for the new features that the latest GA provides :

Introduction As previously explained, CDC (Change Data Capture) is one of the best ways to interconnect an OLTP database system with other systems like Data Warehouse, Caches, Spark or Hadoop. Debezium is an open source project developed by Red Hat which aims to simplify this process by allowing you to extract changes from various database … Continue reading How to extract change data events from MySQL to Kafka using Debezium →

As you may know by now, MySQL 8.0.2 DMR is out ! \o/

Many features have been added (see Geir Høydalsvik‘s announcement) and of course the replication also brought new features and improvements (see this post from Luís Soares).

But some improvements in the monitoring broke the added sys view used by ProxySQL to monitor the state of a member of the group:

mysql> select * from sys.gr_member_routing_candidate_status;
+------------------+-----------+---------------------+----------------------+
| viable_candidate | read_only | transactions_behind | transactions_to_cert | …

The MariaDB project is pleased to announce the immediate availability of MariaDB 5.5.57. This is a stable (GA) release. See the release notes and changelog for details. Download MariaDB 5.5.57 Release Notes Changelog What is MariaDB 5.5? MariaDB APT and YUM Repository Configuration Generator Thanks, and enjoy MariaDB!

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