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?

Two Singaporean brothers turns unsolvable math into post-quantum encryption

Show HN: Ziex, a Zig web framework reaching its first release

Moebius: 0.2B image inpainting model with 10B-level performance

Trump unveiled Qatar's gifted Air Force One this week

Tesla driver says it was on Autopilot before fatal Texas home crash

AI Is Boosting Productivity at Home – But Not Equally

Alan Greenspan's Essay: "Gold and Economic Freedom"

Ask HN: Is there still value in making apps?

AI effect: People are taking up skills for no money, just to feel human

China Became an Energy Superpower [video]

Robotic exoskeleton could redefine how stroke survivors relearn to walk

Polaris: A Native macOS App for Kamal

Hacker News Games in Videos

Extreme Dynamic Symmetry Enables Omnidirectional and Multifunctional Robots

Fungus-Growing Ants

AI will create more jobs for humans, not replace them, says Bezos

QSOE: QNX-inspired OS with dual-kernel architecture

Never Give Them Your Face

Former Unreal Engine 'Lead Evangelist' Sjoerd De Jong Leaves Epic Games

Show HN: GeoTag Photos – Add GPS coordinates to photos in the browser

Why European housing politics should be Americanized

Retrieval Debt: The Technical Debt Your Agent Is Paying

The Coming Enshittification of AI

Have Data Centers Raised Your Electric Bill? Causal Evidence from the US

DNA from 2k-year-old grape seeds points to origins of modern winemaking

Keogram: The Sky in 2025

Chevron signs 20-year power agreement with Microsoft for West Texas data center

Is Time Slowly Dying?

Pledging Another $400k to the Zig Software Foundation

Domain Understanding Is Moat