The latest from the MySQL community

When you rebuild a table with MySQL’s Online DDL, the operation can fail partway through with a Duplicate Entry error:

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mysql> alter table tt add c3 int, algorithm=inplace;
ERROR 1062 (23000): Duplicate entry '1' for key 'tt.uk_c2'

This is a long-standing, well-known problem — it has existed ever since Online DDL was introduced in MySQL 5.6, and it appears across several bug reports:

• BUG#76895 — Adding new column OR Drop column causes duplicate PK error
• BUG#77572 — The bogus duplicate key error in online ddl with incorrect key name
• BUG#98600 — Optimize table fails with duplicate entry on UNIQUE …

Building a Database DBA Lab with Docker, PostgreSQL, MySQL, and Percona Monitoring and Management

How I built a local database playground, learned a few lessons the hard way, and created a practical command reference along the way.

Introduction

One of the best ways to learn database administration is to get your hands dirty.

Documentation is important, but there’s something different about building your own environment, breaking it, troubleshooting it, and eventually understanding why everything works.

Recently, I decided to create a local database lab using Docker Desktop on my Mac. My goal was straightforward: build an environment where I could experiment with MySQL, PostgreSQL, Percona XtraDB Cluster (PXC), and Percona Monitoring and Management (PMM), without worrying about disrupting a production environment.

What started as a few containers quickly became a much more …

Step 3: Why my sysbench-trained build loses and how to do it right.

Given the topic complexity and the length of this article I have split it in 3 three different blog-post:

1. What is PGO
2. How PGO it works
3. Why my sysbench-trained build loses and how to do it right.

Three compounding reasons:

1. Uncovered code gets pessimized.
   Sysbench-tpcc touches a narrow slice of mysqld.
   Every function with zero counts is treated as cold: GCC optimizes it for size, skips inlining, and shoves it into cold sections.
   But at runtime I still execute plenty of code my training never touched, such as purge, flushing, stats …

In our previous blog post ProxySQL HA with BGP ECMP Anycast, we established why we would want to use BGP ECMP as a strategy for making our ProxySQL cluster highly available. Now let’s look at how to implement it technically.

For this scenario we assume that we have:

• an OPNsense instance as our BGP Router with the IP address 10.5.8.251
• Two ProxySQL nodes (proxysql-01 with IP 10.5.20.4 and proxysql-02 with IP 10.5.20.5)
• 10.5.200.1 as the anycast IP we want both ProxySQL nodes to accept connections on

Setup on the router Enable BGP on OPNsense

The out-of-the-box installation of OPNsense does not come with BGP support. To add it, install the FRRouting package first (os-frr), which will enable …

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MySQL News

Note: Aggregated MySQL news can be found at Planet for MySQL Community and Planet MySQL (Oracle curated)

Thread Pool in Percona Server and MySQL (Part 1)
Percona Blog

TL;DR - MySQL 26.7.0 and 9.7.2 bring a thread pool to Community Server for the first time.

…

Step 3: Why my sysbench-trained build loses and how to do it right.

Given the topic complexity and the length of this article I have split it in 3 three different blog-post:

1. What is PGO
2. How PGO it works
3. Why my sysbench-trained build loses and how to do it right.

Three compounding reasons:

1. Uncovered code gets pessimized.
   Sysbench-tpcc touches a narrow slice of mysqld.
   Every function with zero counts is treated as cold: GCC optimizes it for size, skips inlining, and shoves it into cold sections.
   But at runtime I still execute plenty of code my …

A status with angle brackets appears as text in the feed rather than turning into page markup. I appreciate that line breaks also stay visible, so a longer update reads more like what was typed. A submitted status gives you a concrete path into the feed. See how the app saves that update so the […]

OCI Open Source Service Update – Sept. 2026
Explore how MySQL HeatWave on Oracle Cloud Infrastructure helps optimize, protect, and scale MySQL applications.
Covers Autopilot Indexing, high availability with automatic failover, managed read replicas, enterprise security, and fast DB system cloning for development, testing, and regional recovery.

The post MySQL HeatWave Core Capabilities (September 2026) first appeared on Data Daz (dasini.net) - Data Systems, AI, and Real-World Insights.

The Model Context Protocol (MCP) has become a standard way for AI agents to discover the tools an application, database, or service offers. Claude Code, Codex, Cursor, Antigravity, et al. can connect to an MCP server, ask it what tools are available, and call these tools instead of figuring out what they can or can't do on the fly or piecing together API calls. Setting up an MCP server for a database usually means running a separate process that holds a database credential and turns tool calls into queries. Then you have another process to deploy, another place a credential lives, and a set of guardrails that sit outside the database.

The vsql-mcp extension from VillageSQL takes a different approach. It puts the MCP server inside the database. Install it, set a handful of global variables, and your MySQL server itself serves MCP over Streamable HTTP from a background …

Before MySQL 8.0, DDL was not crash-safe. There were three main problems:

1. The metadata in the server layer and the metadata/data in InnoDB could become inconsistent.

   The server-layer metadata was stored in files — for example, table definitions were kept in .frm files — while InnoDB kept its own copy of the metadata in its tables. A crash could leave the server-layer metadata inconsistent with InnoDB’s metadata or even with the table data. For example, the server layer still had the table’s .frm file and believed the table existed, but InnoDB’s .ibd data file was gone, so InnoDB believed the table did not exist.

2. InnoDB’s metadata and data could become inconsistent.

3. The binlog and the data could become inconsistent.

   For example, after a crash and …