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?

OpenAI talent exodus raises 'huge red flag' ahead of IPO

Professor's Death Leaves Behind Hard Questions for Cambridge on Race and Hiring

Show HN: Lots of Agents – Infinite Logged in Grok Bots on One Mac

The Zelda Theme That Changes Every 13.3 Seconds [video]

We built a realtime system for responsive voice AI in six months

Navy weighs major warship redesign to match Trump's preferences

CyberPanel's hard-coded JWT secret grants an unauthenticated root shell

Manipulation versus Management, Tools versus Agents

Parallelism Without Threads [video]

Show HN: Hibi – a calendar app to remember your days

Show HN: GeoLint, an ESLint-style linter for GeoJSON

China is shaping the future of open‑source technology – including AI

Ranking the Most Brilliantly Colored Birds with Data

Go from job search to job offer

Show HN: One question a day for the whole planet, sealed until 20:00 UTC

Show HN: Browser-based Autodesk Inventor file viewer – no Autodesk required

I gave an AI £150 and three months to earn its own subscription

Gmail attachment IDs are not stable (and how they doubled our index)

Amazon bars customers from filing lawsuits

Paper on Architecture for AI-Assisted Software Development

Show HN: A zero-symbol engine to mathematically rank Windows RPC attack surface

YACS 2.0 – Yet Another Curta Simulator

Make Claude Say Less

A Spectre Is Haunting Unicode

Venn Diagram of the Internet

EPA sued for approving semiconductor chemicals that may pose health risks

Ukraine strikes Russia's only Soyuz rocket plant with Flamingo missiles

Gen Z has rediscovered the joy of going to the movies

The Mystery of Dark Oxygen

Qwen3.8-27B – Release Day Demos