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

1•LawZiL•6mo 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•6mo 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•6mo 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•6mo 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•6mo ago

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

To boost research, states are building their own AI-ready supercomputers

A Fasting-Style Diet Seems to Result in Dynamic Changes to Human Brains

Queensland Museum accused of misleading teachers and children about climate

IntelliJ Scala Plugin 2025.3 Is Out

Russia Loses Launch Capability After Accident at Baikonur Cosmodrome

TurtleStitch – Coded Embroidery

The Internet forgets, but I don't want to

Clip of a Tesla Optimus teleoperator taking his headset off

Google is experimentally replacing news headlines with AI clickbait nonsense

How to Articulate Yourself Intelligently

Catala – DSL for deriving algorithms producing automated legal decisions

Ask HN: What's this EU startup that claims its chip is better than Nvidia's?

F Prime

How Docker Works

The Good, the Bad, and the Search:The Golden Era of Spaghetti Westerns 1964-1978

Scratch for Business Process Automation

Show HN: Global crowd-sourced WiFi Speed Map

One too many words on AT&T's $2k Korn shell and other Usenet topics

WebGPU is now supported by all major browsers

Contact Sheet Prompting

It Is Worth It to Optimize Images for Your Site

I tried 'blood cleaning', the latest wellness fad

Show HN: Vibe Code WordPress Plugins

China's exports top expectations on strong sales to non-US markets

I fired myself and made Gemini 3 the CEO of my dying startup

Zono: World Clock Time Zone

Galileo (Operating System)

Introduction

12 Days of Shell

CLI coding agents browsing ncdu/gdu directly instead of parsing JSON