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

1•LawZiL•8mo 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•8mo 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•8mo 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•8mo 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•8mo ago

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

CPython Internals Explained

The Law of Imposter Systems

NDL: Simplifying Local Development for Distributed Systems

The age of Pump and Dump software

Chatuino: A Feature-Rich TUI Twitch IRC Client

Ask HN: Where's the actual pain in early-stage medical AI startups?

I stopped using dependencies and started generating code

Italians furious over deployment of ICE to bolster US security at Olympics

Show HN: CUGA – Configurable Generalist Agent (HuggingFace Live Demo)

Hit21 v1.9

Show HN: We Built the 1. EU-Sovereignty Audit for Websites

Show HN: Terminal style start page for bookmarks and open tabs

I built a C++ runtime with immutable objects and no GIL

Realism vs. style in AI image models (lessons from building a wallpaper app)

Not One Penny

Show HN: IOPS Profiler – Jupyter magic to measure I/O operations per second

Feeds of New EBooks

Vibe Coding Is Free – Cleanup Won't Be

Ancient infection disabled gene in chimp brains that remains expressed in humans

I quit tech today, warning to junior and mid-level devs

Show HN: WhyFi – Figure out why your Wi-Fi is bad and fix it

Doom in the Terminal

Show HN: Build Web Automations via Demonstration

Show HN: Lichess.el – Play Lichess Inside Emacs

Digital Excommunication

Show HN: MonsterWriter – An Overleaf Alternative with a Better Free Plan [video]

Generate HTTP server and client from protobuf

Apple's AirTag 2 is easier to find thanks to new chip

A proposal to prevent job losses from AGI

TikTok users can't upload anti-ICE videos. The company blames tech issues