Where database blog posts get flame-broiled to perfection
Oh, wonderful. A new blog post meticulously detailing how the next-generation database we've been promised will "simplify our stack" is, in fact, slower. I'm so glad someone ran benchmarks in a sterile lab to confirm what my battle-scarred intuition has been screaming for weeks. "I need to change that claim," he says. You think? I have a closet full of free startup t-shirts from companies that had to "change that claim" right after we bet our entire infrastructure on them.
Let me guess, the performance regression is only for "write-heavy tests." You mean, the part of the database that actually does the work? The part that processes user signups, transactions, and every other critical path that keeps the lights on? Shocking. A mere 15% less throughput on the 24-core server. That’s fantastic. My manager will be thrilled to hear that our upgrade to MySQL 9.5 comes with a free, automatic 15% reduction in efficiency. It's not a bug, it's a synergistic de-optimization.
And the cause is just beautiful. The new default settings, gtid_mode and enforce_gtid_consistency, are now ON. A silent, little change in the defaults that just happens to tank performance. This gives me a warm, fuzzy feeling, a nostalgic flashback to that time a "simple" Postgres extension update changed a query planner default and turned our main dashboard's p99 latency from 200 milliseconds to 45 seconds. The on-call alert just said "slowness." The PTSD is real. I can still taste the cold 3 AM pizza.
The regressions are larger when gtid_mode and enforce_gtid_consistency are set to ON
You don't say. So the feature designed for more robust replication and consistency—you know, the entire reason we'd even consider this painful migration—is what makes it slower. It's like buying a sports car and finding out the engine only works if you keep it in first gear. This is perfect. We can have the shiny new version number, as long as we turn off the shiny new features.
I love the clinical breakdown here. The lists of hardware, the eight different versions tested for every permutation of -gtid and -nogtid. It’s like a horror movie where the scientist calmly documents every new way the monster has learned to kill.
8.0.44-nogtid: The good old days, when things just worked.9.5.0-gtid: The future, where CPU usage is higher, context switches are through the roof, and we write more to disk for the privilege of doing less work.Look at these metrics, they're poetry. "Context switches per operation (cs/o) are 1.26X larger." That's not just a number. That's the sound of my PagerDuty alarm. That's the ghost of a future incident report I'll have to write, explaining why our "upgraded" database is spending all its time thrashing instead of serving queries.
My absolute favorite part is this little gem:
This result is odd. I might try to reproduce it in the future.
Oh, you might? That’s fantastic. Don't worry, I'm sure we'll reproduce it for you. At peak traffic. On a holiday. When the one person who understands that subsystem is on a flight with no Wi-Fi. That "odd result" is the gremlin that will live in our system for the next six months, only showing up under a full moon and causing cascading failures that nobody can explain. And then some VP will ask why our cloud bill is 20% higher. Because we're paying for more "CPU per operation," my friend. We're paying for the innovation.
So, thank you for this incredibly detailed roadmap of my next year of sleepless nights. It's great to see all the new and exciting ways this "simple" version bump is going to create a whole new class of problems for me to solve, while management celebrates the successful migration.
Anyway, I'm going to go ahead and bookmark this. Just kidding. I'm closing this tab and will do my absolute best to forget I ever saw it.