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

1•LawZiL•7mo 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•7mo 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•7mo 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•7mo 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•7mo ago

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

Grilli Type

Generative UI from Gemini 3 Pro

What can I do with ReScript?

Runaway Tokens (A Postmortem)

Audio Frequency-Time Dual Domain Evaluation on Depression Diagnosis

Ford Considers Scrapping Electric Version of F-150 Truck

A Better Judging Algorithm for the Largest Hackathon in Wisconsin

The Stalled Charge:What Cutting EV Funding Means for the US Infrastructure Map

Show HN: Blog post runs P2P from my laptop

LG TV users baffled by unremovable Microsoft Copilot installation

Dawn: A distraction-free CLI writing env with live Markdown rendering

PSA's parent company Collectors acquired Beckett to consolidate hobby market

Security at Blacksmith

Researchers reveal bias in a widely used measure of algorithm performance

Generalized String Art Generator (2023)

Do LLMs Understand? AI Pioneer Yann LeCun Spars with DeepMind's Adam Brown [video]

Publisher under fire after 'fake' citations found in AI ethics guide

Ask HN: Should the Only Christian Have to Work on Christmas Day

Virustotal: R Client for the VirusTotal Public API v3.0

Show HN: Go Libraries for Working with OpenAPI

nowindows

UK to "encourage" Apple and Google to put nudity-blocking systems on phones

CMYK Simulator

Amazon's Aggressive Push to Get Cops Using AI Surveillance

Ukrainian Security Service Struck the Varshavianka (Kilo) Submarine

Killed by Google

I made a network throttle tool controlled by a Chrome extension

Full screen ads in iOS at OS level interactions

Designing a Passive Lidar Detector Device

What's the point of lightweight code with modern computers?