Ask HN: How can I load test PostgreSQL but avoid changing actual data?

1•LawZiL•1y ago

I'm running a load test on my Node.js application and want to simulate realistic write-heavy scenarios to stress test the system — especially the PostgreSQL database.

There's a part of the code that performs UPDATE queries, but during load testing, I don't want these updates to actually change the state of the database. However, I still want the database to experience the full impact of the update — query planning, locking, I/O, WAL writes, etc. — so I can measure how it affects performance under peak load.

Is there a best-practice approach to achieve this?

So far, the most viable option I’ve found is to wrap the UPDATE queries in a transaction and then roll it back — that way, the queries still execute, but the state doesn’t change. Is this the right way to go? Does rollback introduce any performance overhead that would skew my results? Are there better or more realistic alternatives that simulate the full write path without persisting changes?

Thanks in advance!

Comments

sargstuff•1y ago

pgbench[2] / pgreplay-go[0] / python locust[1]

very old school approach:

Misuse sql VIEW[3][4] to generate a temporary parallel table setup. Testing database separate from production database would be 'better', IMHO.

-----

[0] pgreplay-go : https://github.com/gocardless/pgreplay-go

[1] python locust : https://miguel-codes.medium.com/unconventional-load-testing-...

[2] pgbench load testing :

   a) https://medium.com/@c.ucanefe/pgbench-load-test-166bdfb5c75a

   b) https://neon.tech/blog/autoscaling-in-action-postgres-load-testing-with-pgbench

   c) https://hackernoon.com/how-to-create-and-load-test-data-in-postgresql-i41e353m

----------------------------

[3] : a) https://hashrocket.com/blog/posts/materialized-view-strategi...

      b) https://tech.jonathangardner.net/wiki/PostgreSQL/Materialized_Views

      c) https://stackoverflow.com/questions/77603705/what-is-the-use-of-materialized-view-in-postgresql

[4] : https://en.wikipedia.org/wiki/View_(SQL)

LawZiL•1y ago

but again, how can i perform the query, but not actually change the state, i really need the state to keep untouched, but be able to perform the query itself.

MatthiasPortzel•1y ago

> Does rollback introduce any performance overhead that would skew my results?

I would expect it to be the other way around—since the transactions are rolled back and not committed, they would have significantly less performance impact. But I’m working from an academic model of the database.

apothegm•1y ago

Load test against a clone instead of a DB whose contents you care about?

AWS Lambda Web Functions

The First Social Network

They War-Gamed Dimming the Sun. It Went Worse Than You Think

NASA may have proof life once existed on Mars

Lever House

Voyager Earth – animated travel route maps rendered in the browser

The Tetrad Tour, Part III: Why AI Needs Its Linnaeus

An Industrial Policy for Drones

Neocloud Endgame

Empirical Computation: Prompting versus Programming [pdf]

Japan declares a "state of emergency in cyberspace" as cyberattacks surge

Claude Notify – Desktop Notifications for Claude Code on Windows

Portless: Vercel Labs Replaces Localhost Ports with Named URLs

Ukraine strikes didn't blow up Russian disinformation on social

Breaking Bad star RJ Mitte dies aged 34

RenkuOS (A Fork of Haiku)

What I've been seeing lately

Adm Programming Language

Patching Zig's Std

UK data centre giant removed evidence of China deal ahead of $35B listing

What the Greeks Would Call Our Government [video]

Orion2re: A restoration effort for the Master of Orion II game engine

AI's mathematics blitz pushes science into new territory

Agentic BSS Explained: AI-Native Model, Architecture and Use Cases [pdf]

Janas: Run LLMs larger than RAM by streaming experts from SSD

The CEO's of Broadcom and Intel Say the Quiet Part Out Loud about AI and ROI

Making DNA: The Quest for Synthetic Life (2023)

Mozilla Welcomes Raffi Krikorian as Chief Technology Officer

Artificial Intelligence in the Firm: Bottlenecks in Software Production [pdf]

Using Jev to make your agents write the code and design the app the way you do