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?

Self-Hosting WordPress Course

Greeting Vocalizations in Domestic Cats Are More Frequent with Male Caregivers

From the Grid to the Prompt

Grok: 'It's basically the curlable Résumé.'

Study: Effects of LLMs versus Web Search on Depth of Learning

Managing Postgres Extensions with ImageVolume

DiskBBQ – Elasticsearch's vector storage format

Docker Compose Models Explained

Yoloe: Real-Time Seeing Anything

Putting email in its place with Emacs and Mu4e

Postgres CDC in ClickHouse, A year in review

Constructing a JPEG XL MD5 hash quine

NASA Rover Detects Electric Sparks in Mars Dust Devils, Storms

3D-Printed Carotid Artery-on-Chips for Personalized Thrombosis Investigation

IoT and AI-driven solutions for human-wildlife conflict

Support Techdirt's Uncompromising Coverage, Get Our First Commemorative Coin

Trump Returns to Gasoline as Fuel of Choice for Cars

Using AI to generate alt text for 27000 images

City Of Winter: A roleplaying game about a fantastical family saga

Ragas: Automated Evaluation of Retrieval Augmented Generation

Show HN: Cross-platform network traffic monitoring system

Show HN: Rust Client Library for Gradium.ai TTS/STT API

RISC-V Oral History Panel [video]

Cloudflare Timeouts in Europe

Trump admin funds geothermal network expansion

Making Friends with Foreigners

Developing a New Electric Vehicle Sound

The framework isn't for you. You're just along for the voyage

"Netflix killed casting from phones"

I ran out of money, spent my savings on a Hong Kong prostitute,& became a commie