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?

YouTube Had a Bug – I Used ChatGPT to Investigate

Casio 'CasioNaut' G-Shock GMC-2500 GAC-2500 Series: Price, Specs, Availability

Any Nix package, live in the browser

Tinymongo

GitHub Status – Disruption with Copilot Code Review

Where Will RISC-V Be in 20 Years? Poll Results

Show HN: Layerz – Native App Designer

Bitcoin mining data center condemned after leaking 3M gallons of water

How algorithms are making our environments bland

An off the self BYOA platform

The Man That Invented the Popup

Washington Post says Piker used AI generated audio but admits it has no proof

All of Claude's "Never Do This" in Fable 5.1 System Prompt

Connecting Kubernetes dependencies to application telemetry

Big Brother is going to college: The federal plan to track students for life

Apex City – Build a city that works

FDA Recalls IV Fluids over Possible Fiberglass, Stainless Steel Contaminants

The Association for Computational Heresy

Apple and Atari Connections – By Paul Lefebvre – Goto 10

Ask HN: (Why) Was the LLM breakthrough useful for images, audio, etc.?

Jelly Baby

Guess the Song in 0.1 Seconds

Sunday programmer emergency: production is down. (quiz)

OpenAI: We monitor internal coding agents for misalignment

Big brother watch report reveals free speech is in "downward spiral" in the UK

Feature complete, as long as you add more features

Show HN: Robot-duck soccer in the browser, powered by MuJoCo and learned walking

.gitignore Generator by Codra

Homelab deployments: a tutorial made of prompts

Ask HN: How to prepare for coding/system design interviews on a mobile phone