Software development is always moving forward, and the latest version is always the best ... until the next one arrives.  When you visit the MySQL Ndb Cluster downloads page, you are naturally recommended to pull the latest MySQL Cluster 8.0.22 (announcement), but sometimes it is good to look back at the journey taken to reach this point.

7.x release series

Prior to the 8.0 releases, MySQL Ndb Cluster had a sequence of 7.x (x=0..6) releases based on MySQL Server versions 5.1, 5.6, 5.7.  In each of the 7.x release series, MySQL Ndb Cluster was under feature development for some time, producing a number of minor releases, until eventually one minor release was validated as being acceptable as the first generally available (GA) …

In a perfect world, we expect all software to run flawlessly and never have problems such as bugs and crashes. We also know that this perfect world doesn’t exist and we better be as prepared as possible to troubleshoot those types of situations. Historically, generating core dumps has been a task delegated to the kernel. If you are curious about how to enable it via Linux kernel, you can check out Getting MySQL Core file on Linux. There are a few drawbacks that pose either a limitation or a huge strain to get it working, such as:

• System-wide configuration required. This is not something DBA always has access to.
• Inability or very difficult to enable it for a specific binary only. Standards ways enable it for every software running on the box.
• Nowadays, with cloud and containers, this task has become even …

For what reason should I use a real multi-Primary setup?
To be clear, not a multi-writer solution where any node can become the active writer in case of needs, as for PXC or PS-Group_replication.
No, we are talking about a multi-Primary setup where I can write at the same time on multiple nodes.
I want to insist on this “why?”.

After having excluded the possible solutions mentioned above, both covering the famous 99,995% availability, which is 26.30 minutes downtime in a year, what is left?

Disaster Recovery? Well that is something I would love to have, but to be a real DR solution we need to put several kilometers (miles for imperial) in the middle. 

And we know (see here and …

Many times, we do not want duplicate rows or values in our SQL tables. On the other hand, in some situations, it does not matter if there are duplicates present. For whatever reason, suppose duplicates have found their way into one of your tables. How can you find them quickly and easily? The ROW_NUMBER() Window function is a fantastic tool to use. Continue reading and see example queries you can apply to your own tables and find those duplicates…

Photo by Joe Green on Unsplash

OS and DB used:

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This blog discusses new features about the persisted system variables and how we can use it to make variable changes persistent. The MySQL server maintains system variables that control its operations. The dynamic variables used prior to the MySQL 8 release are not persistent and are reset upon restart. These variables can be changed at runtime using the SET statement to affect the operation of the current server instance but we have to manually update my.cnf config file to make them persistent. In many cases, updating my.cnf from the server-side is not a convenient option, and leaving the variable just updated dynamically reverts on the subsequent restart without any history.

Persisted system variables are one of the useful features introduced in MySQL 8. The new functionality helps DBAs update the variables dynamically and register them without touching the configuration files from the server-side.

How to Persist the Global …

If you often deploy services in the cloud, you certainly, at least once, forgot to stop a test instance. I am like you and I forgot my share of these. Another mistake I do once in a while is to provision a bigger instance than needed, just in case, and forget to downsize it. While this is true for compute instances, it is especially true for database instances. Over time, this situation ends up adding a cost premium. In this post, we’ll discuss a solution to mitigate these extra costs, the use of the RDS Aurora Serverless service.

What is Amazon Aurora Serverless?

Since last spring, Amazon unveiled a new database related product: RDS Aurora Serverless. The aim of this new product is to simplify the management around Aurora clusters. It brings a likely benefit for the end users, better control over cost. Here are some …

MySQL 8.0.22 was released on Oct 19, 2020, and came with nice features and a lot of bug fixes. Now, you can configure your async replica to choose the new source in case the existing source connection (IO thread) fails. In this blog, I am going to explain the entire process involved in this configuration with a use case.

Overview

This feature is very helpful to keep your replica server in sync in case of current source fails. 

To activate asynchronous connection failover, we need to set the “SOURCE_CONNECTION_AUTO_FAILOVER=1” on the “CHANGE MASTER” statement.

Once the IO connection fails, it will try to connect the existing source based on the “MASTER_RETRY_COUNT, MASTER_CONNECT_RETRY”. Then only it will do the failover. 

The feature will only work when the IO connection is failed, maybe the source crashed or stopped, or any network failures. This will not work if the replica is …

I am always surprised to learn something new whenever I talk to a member of the open-source community. No matter how much I think I have heard of every use case there is for Liquibase (and database change management in general), I always hear something that makes this space still feel new. There’s always something left to discover.

Today, that new something is the problem of how to perform large batches of changes with SQL ALTER TABLE statements. No problem you say? Okay, but this ALTER needs to happen in production. Still not worried? Well, let’s say you have millions of rows, and because you’re so successful, you have many transactions happening per minute (maybe even per second). Yeah…now we are talking. You can’t alter the table because you can’t afford to lock that table for the …

The amount of transactions committed is an important information, but how could you return an accurate value?

This is a question I got from my colleague Ivan, he was challenging with global status values like COM_COMMIT or HANDLER_COMMIT, then checking in innodb_metrics… but this was not accurate.

In fact depending which storage engine you are using, if binary logs are enabled, if you rollback transactions, if you are using auto_commit, etc… all those parameters influence those values.

So the first question was “What metrics or else should we use ?”. In my opinion, the most accurate “counter” for transactions are the GTIDs.

And this is why I created yet another MySQL Shell plugin that does that calculation:

This plugin is available on my GitHub repository …

Earlier this week, Oracle released their Q4 releases series. As on the previous releases, backward compatibility has been broken with previous versions of the server. This time on both MySQL 5.7 and 8.0:

MySQL 5.7.32

While our QA team was performing an extensive test on it,  we found out this version introduced a new compression format version. This change breaks backward compatibility with older versions of MySQL, which is expected on the 8.0 series but is not on 5.7. As Percona XtraBackup (PXB) is based on MySQL code, it makes MySQL 5.7.32 incompatible with current versions of Percona XtraBackup 2.4.20 and prior.

The issue does not affect only Percona XtraBackup but also prevents users from downgrading the server from 5.7.32 to any lower version on the 5.7 series – More details at …