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

1•LawZiL•11mo 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•11mo 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•11mo 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•11mo 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•11mo ago

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

Indent Is All You Need

The arrogant superbanker whose hubris brought Britain to its knees

Making the Rails Default Job Queue Fiber-Based

The Dirty Little Secret of AI (On a 1979 PDP-11) [video]

HappyHorse AI – AI-Powered Equestrian Training

Master of chaos wins $3M math prize for 'blowing up' equations

Why the Original Task Manager Was Under 80K and Insanely Fast [video]

Influencers Are Spinning Nicotine as a 'Natural' Health Hack

Details that make interfaces feel better

Watch a 200 Pound, 14" Drive from the 80s Boot Unix [video]

My billing system, it could be useful to some

ConvertHook – White-label widget that shows where brands rank in ChatGPT

Palantir manifesto reads like the ramblings of a comic book villain

SUSE and Nvidia reveal a turnkey AI factory for sovereign enterprise workloads

Curlew conservation scheme makes breakthrough in Fermanagh

Modern Front end Complexity: essential or accidental?

Show HN: WeTransfer Alternative for Developers

Keeping code quality high with AI agents

The MACL Extended Attribute

Mother Earth Mother Board

US recession probabilities implied by the yield curve

Show HN: AnyHabit – A minimalist habit tracker for Raspberry Pi and Docker

Highlights from Git 2.54

Enhancing Sporting Organisation Efficiency with Generative AI

Reconstructing a Vue and Three.js app from a single Webpack bundle

Show HN: Tiltbump – another game in a single HTML file

WebP to PNG Converter – Convert WebP to PNG Online Free

AI agents are a security nightmare. Moving the dev workflow to QEMU

Kiss Principle

Pagetok – an all-in-one AI assistant on your Mac