🔥 The DB Grill 🔥

Where database blog posts get flame-broiled to perfection

Explaining why throughput varies for Postgres with a CPU-bound Insert Benchmark
Originally from smalldatum.blogspot.com/feeds/posts/default
February 18, 2026 • Roasted by Sarah "Burnout" Chen Read Original Article

Oh, fantastic. Another deliciously detailed deep-dive into a problem that we're about to voluntarily inflict upon ourselves. I am simply captivated by this discovery of a "distorted sine wave" in performance. It’s not a bug; it's the beautiful, rhythmic heartbeat of my next 72-hour on-call shift. It's the pulsating, problematic pulse of my PagerDuty notifications going off in perfect, terrifying harmony.

I truly appreciate the history lesson on the Insert Benchmark. It's so reassuring to know this entire strategy is based on a C++ benchmark from the TokuDB-era that was then rewritten in Python for convenience. Nothing screams high-performance data pipeline like introducing the Global Interpreter Lock to your stress test. It’s this kind of forward-thinking that has me clearing my calendar for the inevitable 3 AM "simple patch" deployment.

And the new workflow! Genius. We were running out of disk space, a simple, tangible problem with a clear solution: buy more disks. But instead, we've engineered a brilliantly complex system of inserting and deleting at the same rate. We've traded a predictable problem for a fantastically fickle one. It's not about managing storage anymore; it's about managing a delicate, chaotic dance of transactions that will absolutely never, ever get out of sync.

This DELETE statement is a work of art. A true masterpiece of defensive programming that I'm sure will be a joy to debug when it deadlocks the entire table.

delete from %s where transactionid in (select transactionid from %s where transactionid >= %d order by transactionid asc limit %d)

A subquery to find the very rows you want to delete? Based on a guess? This is the kind of query that gives me flashbacks to that "simple" data backfill that caused a cascading replication failure across three availability zones. We're not just deleting rows; we're launching a self-inflicted DDoS attack on our own primary key index.

But of course, the grand reveal, the culprit we all knew was lurking in the shadows: "Once again, blame vacuum."

I am so, so relieved. For a moment I was worried we had discovered a novel, interesting failure mode. But no, it's just good old VACUUM, the ghost in every Postgres machine, causing CPU spikes and performance degradation. We've gone through all this trouble to build a new benchmark and a new workflow, only to run headfirst into one of the most profoundly predictable performance pitfalls in the entire ecosystem. It's like spending a year building a spaceship just to crash it into the moon because you forgot to account for gravity.

So let me get this straight. We're going to migrate to a system where the performance graph looks like an EKG, using a delete strategy that's one part hope and two parts subquery, all built on a foundation that is fundamentally at odds with the database's own garbage collection.

I, for one, can't wait. That distorted sine wave isn't a performance chart. It's a prophecy. It’s showing us the glorious, oscillating waves of failure that will crash upon our production servers. Mark my words, in six months, that sine wave will be the only thing moving on our status page after the whole system flatlines. I'll start brewing the coffee now.