Symlinks are Unsafe since MySQL 8.0.39 (and maybe even before)

You read this right, symbolic links (symlinks) are unsafe in MySQL since at least 8.0.39.  As always, it is a little more complicated than that, but if you are using symbolic links and in certain conditions, you risk a crash.  I think it is important to raise awareness on this, hence this post.

Undo Log Truncation Bug in 8.0 leads to Data Corruption

I am upset about this one : I have a hard time not seeing this as negligence, and it starts to become a pattern...  So please forgive me if this post is not my most diplomatic, because I really think someone deserves a kick in the butt !  But what is all this about...

There is a MySQL bug, which can lead to data corruption, opened for 8.0 in September 2023, fixed in MySQL 8.4.0 (released in February 2024), AND STILL NOT FIXED IN MySQL 8.0.44 !  Luckily for some, it is fixed in Percona Server 8.0.39 (released in October 2024).  As usual, I start this post with some context before diving in the nitty-gritty details.

Duplicate Entry in ALTER TABLE (and in OPTIMIZE TABLE)

A few weeks ago and in MySQL 5.7, I had an ALTER TABLE that failed with a duplicate entry error.  This is old news as it is happening since MySQL 5.6, but I only saw this recently because I am normally using online schema change from the Percona Toolkit (pt-osc) or GitHub's online schema migration (gh-ost).  I do not like that and I am disappointed this has not been improved, so this post is partially a rant, but not only, because I explain why ALTER TABLE is failing and I give solutions to avoid the failure.

The annoyance of the day, brought to you live from the MySQL Ecosystem

And by MySQL Ecosystem here, I do not only include Oracle but also MariaDB.