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

1•LawZiL•10mo 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•10mo 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•10mo 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•10mo 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•10mo ago

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

Adult German men must request permission to leave Germany for more than 3 months

Jj v0.40.0 Released

First MCP server for Guesty property management – 39 tools, open source

Blaming insecurity on consumer Wi-Fi routers on foreign OEMs is a red herring

API for UK waste carrier verification, EWC classification and digital WTNs

I fact-checked Scientific American, with accidental help from Anthropic

Show HN: Replace 6 months of GTM trial-and-error with simulated buyers

Characterizing Abusive IP Proxies [pdf]

I run my company from Emacs

Visualization of Tensors

Show HN: Figma 3D Tilt, Like "Firefox Tilt" but for Figma

Cookslate – Self-hosted recipe manager with Cook Mode and cook journal

The College Student–and His Cat Meme–Who Hunted the Biggest Cyberweapon

Show HN: Reverse-engineered Claude in Chrome after the source leak

Show HN: I built a frontpage for personal blogs

Eating the Web

Student Developer and GSoC '25 Contributor Seeking Intern/Junior Roles

Eddy Chen on the Laws of Physics (2024) [pdf]

Age of Invention: Why Scotland Succeeded

Trial by Fire Onboarding

Show HN: How do you manage multiple AI agents? We built a tmux-based in Rust

Ubuntu now has higher system hardware requirements than Windows 11

DeepFocus-BP: Adaptive backpropagation reducing FLOPs by 66% with accuracy gain

Factoring is not a good benchmark to track Q-day

Chip-8 Emulator from Spec

Google Unveils Restoration of Hangar One in Mountain View

An AI website that tells you what to wear at 0 cost somehow

Service Monitoring of Your Bike

After 17 years, AO3 is exiting open beta

Names of Easter