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 (
A unique constraint specifies, one or more columns as unique it identifies. It is satisfied only when no two rows store the same non-null values at its core. A primary key constraint is a unique one that will say PRIMARY KEY in its defined way. It is satisfied only when rows unfold, and none may […]
In a recent post, The Quirks of Index Maintenance in Open Source Databases, I compared the IO load generated by open source databases while inserting rows in a table with many secondary indexes. Because of its change buffer, InnoDB was the most efficient solution. However, that’s not the end of the story. Evolution of the […]
When you run a simple write, …it may look simple, but under the hood, MySQL’s InnoDB engine kicks off a pretty complex sequence to ensure your data stays safe, consistent, and crash-recoverable. In the top-left corner of the diagram, we see exactly where this begins — the moment the query is executed: [crayon-695d8ceb679f4501850310/] The log […]
I recently troubleshoot an interesting MySQL crash, and I think it is worth sharing (with the related bugs). MySQL crashed when the disk was full, you can see the free disk graph below. The Y-axis is in the tens of GiB scale and the X-axis is in the hour scale. Can you guess what happened ?
Just to make sure we agree on the meaning of the graph above, let's describe it
In this blog, we continue from where we left off in the previous post, InnoDB Cluster Setup: Building a 3-Node High Availability Architecture, where we demonstrated how to set up a MySQL InnoDB Cluster with three nodes to achieve high availability. Here, we walk through the step-by-step process of performing a rolling upgrade of that […]
Setting up an InnoDB Cluster requires three key components: Group Replication, MySQL Shell, and MySQL Router. In the previous post, we covered the process of building a 3-node InnoDB Cluster. In this post, we shift our focus to configuring MySQL Router and validating failover functionality. Environment overview We are using three InnoDB Cluster nodes along […]
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 Performance Regression from 5.7 to 8.0 on ALTER TABLE FORCE). There has been recent activity on this bug, showing an easy workaround. This, even if it is known since 16 July 2024, has not been talked about much, so this deserves a blog post.
When performing backups, reducing the amount of time your server is locked can significantly improve performance and minimize disruptions. Percona XtraBackup 8.4 Pro introduces improvements in how DDL (Data Definition Language) locks (aka Backup Locks) are managed, allowing for reduced locking during backups. In this post, we’ll explore the impact of these enhancements. TL;DR (Summary) […]
As promised, my slides from FOSDEM25 and Pre-FOSDEM MySQL Belgian Days :
And since I was asked several times about MySQL test case demonstrating glibc-malloc memory fragmentation / leaks -- here are all the details :
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