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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 …

Step 2: How it works

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.

How PGO works: PGO is a two-pass build. First pass compiles with instrumentation (-fprofile-generate): every basic block and branch gets a counter.
You run a training workload, counters are dumped to profraw files.
Second pass recompiles using those counts to drive inlining decisions, branch layout (hot path falls through, cold path jumps away), hot/cold function splitting, code ordering for icache/iTLB locality, …

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.

Step 1: What is PGO

PGO (Profile-Guided Optimization) is a two-pass compilation technique. 

First, we build the program with instrumentation that adds counters to every branch, loop, and call site.
Next, we run it against a representative training workload so these counters can record which code paths are actually hot versus cold.
We then recompile the program using that data to drive the compiler’s decisions.

With this profiling …

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 …

Ask anyone who runs a multi-node MySQL Galera Cluster in production about their worst night. Almost nobody says write-set replication was wrong. They say something closer to this:

“All queries piling up… no error messages in logs.”

Twenty minutes of downtime, ended only when a human picked a node to kill. (codership-team)

Or the flow-control stall where writes time out and wsrep_flow_control_sent still reads 0, so there’s nothing to alert on and nothing to write in the post-mortem. (codership-team)

You have your own version of these. You didn’t need mine.

And here’s the thing about all of them: the root cause is usually not Galera. It’s flashcache, or a shadowed wsrep_provider_options line, or DNS resolving to …

In the first post in this series, we configured MySQL Telemetry to export OpenTelemetry metrics to Prometheus. Once the metrics arrive, the more important question is how a DBA should read them. This post is not a catalogue of every metric or meter. Its purpose is to build a practical way of thinking: start with […]

At a recent discussion with MySQL ACEs and Rockstars, we were asked a fair question: If a bug is fixed in one supported MySQL LTS series, why isn’t it always fixed in another? A quick refresher: LTS means Long-Term Support. Within an LTS series, MySQL aims to keep the feature set and data format stable […]

MySQL is very good at serving application workloads, but things get more complicated when somebody decides to run a large report on the same server.

A scan can push hot pages out of the buffer pool. A long-running read can hold back purge. A GROUP BY over millions of rows can start writing temporary tables to disk.

The traditional answer is a reporting replica. But that means running another MySQL server, and at the end of the day it is still a row-oriented database.

Another option is moving the data into an analytical database. That can work very well, but now you have a data pipeline to build, operate, monitor, and eventually debug.

We have been looking at what MySQL users can do with DuckDB, and DBTrail is an interesting approach.

DBTrail is open source under Apache 2.0. It is being built by Daniel Guzman-Burgos, who previously worked at Percona as a MySQL Technical Lead.

…

Type “a heist that goes wrong in a snowy town” and get back real films, with posters, in a few milliseconds. The vector search behind it runs inside MySQL, with no separate vector database.

Movie Finder is the new demo app that ships with MyVector. It searches up to 1,035,695 TMDB movies by meaning, not keywords. One docker compose up gives you the whole thing: MySQL 9.7 with the MyVector component, a loader, and a small web app.

Try it live: https://demo.myvector.online/

We built it to answer the questions people ask us most. Does vector search in MySQL hold up at a million rows? Can I mix it with ordinary WHERE filters? What happens when I insert a new row? The demo shows the answers on the page, with the SQL that ran under every result.

Live: What you can do on the page

Every feature on the …

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 …