J-F Gagné's MySQL Blog

I recently troubleshoot an interesting MySQL crash, and I think it is worth sharing (with the related bugs).  MySQL crashed when the disk wa...

As I wrote in a LinkedIn post , I am working on a blog post related to binary logging of big transactions.  I thought I would split this pos...

While doing benchmarks on 5.7 and 8.0, I came across a performance regression in MySQL 8.0 over 5.7 and opened a bug ( Bug #111353 : 3x Perf...

I just submitted a MySQL Contribution and I would like to gather feedback about it.  Depending on the received feedback, I might submit an u...

In the last weeks / months, I have been working on understanding / improving MySQL startup with many tables.  I already wrote five posts on ...

I am writing this quick post to share what I think is a problematic new behavior of Offline Mode in MySQL 9.  Basically, the new default beh...

In the last weeks / months, I have been working on understanding / improving MySQL startup with many tables.  I already wrote four posts on ...

This post is a little long, please bear with me as after the intro, you can skip to the essential. In the last weeks / months, I have been w...

In the last weeks / months, I have been working on understanding / improving MySQL startup with many tables.  I already wrote two posts on t...

In the last weeks / months, I have been working on understanding / improving MySQL startup with many tables.  I already wrote a post about m...

I have been scratching my head about MySQL startup for some time.  There is much to say about this, and many other posts will probably follo...

When running tests, it is sometimes useful to slow down IOs to clearly show the impact of reading from the disk.  Modern laptops and servers...

Yes, you read this correctly: because the MySQL client is insecure and allows running arbitrary commands, and because mysqldump blindly trus...

A month ago, I announced that I am working on a MySQL Contribution to add database / schema in the slow query log file ( bug report , Linked...

Yes, this is a catchy title, but it is true, and it got you reading this post :-).  Another title could have been “Please load this mysql-du...

Not very long ago (well, maybe a little longer, this post is in draft for more than a year), in the spawn of less than 5 days, I suggested m...

A few days ago, Oracle released three new MySQL GA versions : 8.2.0, 8.0.35 and 5.7.44.  I skimmed the release notes ( 8.2.0 , 8.0.35 and 5...

When trying to understand queries in the slow log, an interesting metric to look at is rows examined .  Also, when trying to understand CPU ...

I am finalizing my Percona Live talk MySQL and Vitess (and Kubernetes) at HubSpot .  In this talk, I mentioned that I like that Percona is p...

I just booked my travel arrangements for Percona Live 2023 .  In case you missed it, one of the most important MySQL Conference of the year ...

In May 2020, I published a Planet for the MySQL Community Pluto Beta .  I was satisfied with the result and was considering it done , but I ...

In my previous post about InnoDB Stalls on Empty Free List , I used a test environment that might look a little artificial : a table larger ...

If, in Percona Server, you are observing tail latencies on queries that should be fast, this might be a side effect of Percona's improve...

Sometimes, the MySQL Optimizer chooses a wrong plan, and a query that should execute in less than 0.1 second ends-up running for 12 minutes ...

I am currently working on a script to auto-enable parallel replication / multi-threaded replication ( MTR ) when there is replication lag.  ...

When Index Condition Pushdown is used, you cannot trust rows examined as reported by the slow query log (nor in some Performance Schema tabl...

A year ago, I blogged about An Unprivileged User can crash your MySQL Server .  At the time, I explained how to protect yourself against thi...

I created the first draft of this post many years ago.  At that time, I was working with physical servers having 192 GB of RAM or more.  On ...

A year ago, I blogged about An Unprivileged User can Crash your MySQL Server .  At the time, I presented how to protect yourself against thi...

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...

At my FOSDEM talk earlier this year, I gave a trick for fixing a crashed GTID replica.  I never blogged about this, so now is a good time.  ...

Yes, your read the title correctly: an unprivileged user can crash your MySQL Server.  This applies for the default configuration of MySQL 8...

Three weeks ago, I released the Pluto Beta of Planet for the MySQL Community .  Since then, a few things changed and I think it is worth doi...

As indicated in a previous post, I am working on Planet [for the] MySQL Community for which I did a RFC on the Requirements .  I am happy t...

As indicated in a previous post, I am working on a Planet MySQL Community (this name is not final, see below).  In this post, I want to pre...

Oups, my previous post had a forbidden word and did not show-up on Planet MySQL, so retry... As written in a previous post,  the state of...

As written in my previous post, the state of Planet MySQL is unhealthy  !  I am still aggregated there for now as, before leaving what was ...

Also, the state of bugs.mysql.com: unhealthy (last paragraph below, but this would be too long a title). I have been complaining for some ...

Update 2020-05-05 : I stopped providing consulting hours.  They were not very popular, but it was worth trying. We are all impacted by COV...

In my previous post ( Puzzled by MySQL Replication ), I describe a weird, but completely documented, behavior of replication that had me scr...

Recently, I was puzzled by MySQL replication !  Some weird, but completely documented, behavior of replication had me scratching my head for...

There is an interesting feature in MySQL 5.7+: the global variable super_read_only .  MySQL 5.6 and before only had the read_only global va...

This is a follow-up post in the MySQL Master Replication Crash Safety series.  In the previous posts, we explored the consequences of reduci...

This post is a sister post to MySQL Master Replication Crash Safety Part #5: making things faster without reducing durability.  There is no ...

This is a follow-up post in the MySQL Master Replication Crash Safety series.  In the three previous posts, we explored the consequence of r...

This post is a sister post to MySQL Master Replication Crash Safety Part #4: benchmarks of high and low durability .  There are no introduct...

I am currently running tests with sysbench  and  dbdeployer on a Google Cloud Platform Debian 9 instance.  I ran into an interesting limit...

When creating a MySQL CloudSQL instance, SSL connections are not enforced by default and you get below in the Connections tab of the Goog...

War story of the day: do not use — or be very careful when using — the max_connections beta database flag on CloudSQL ... because it has man...

Some months ago, Shlomi Noach published a series about Service Discovery .  In his posts, Shlomi describes many ways for an application to f...