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?

Show HN: Nearby Share:I built a browser-based file transfer tool

Anthropic IPO meets AI backlash

Show HN: A 40MB TTS model hand-ported to run in the browser (TS and WGSL)

Stock market casino: the rising stakes of 'gamified' investing

European governmental DNSSEC: policy and promotion drive adoption

Ask HN: Will Humans Become Useless?

Endlessly self-injection-locked photonic integrated lasers (2026)

OpenConche: Modern engine for Chocolatier games (2007-2009)

Turn text or photos into 360° panoramas with AI

Tech giant Nvidia to investigate CEO's affair with suspected Chinese spy

The Tragedy of the Oxide Root of Trust

Stop Measuring Developer Productivity

'A new age of climate extremes': Earth accumulating heat at accelerating rate

ESP32 Tailscale gateway with WoL and other recovery functions

Show HN: CodeHub – Turning release notes into pictures so that it is fun to read

Asahi Linux forbids using AI to contribute

IAL Paper Tracker – free tracker for Edexcel IAL students

PixelOS

500 Lines or Less: A Simple Object Model

The Dose Makes the Poison

Making the Iron Giant Live

370 Books in 20 months: South African author defends her use of AI

Tracking AI's Real-Time Footprint on the Labor Market

Next-Concept Modeling: Fast, Parallel Coarse-to-Fine Text Generation

Whoops, I context-switched one too many times

Show HN: Dependency free RSS reader (vibecoded with DeepSeek)

Show HN: Wallpaper that adapts to your icon layout

AML Cycle 2 preview: How well does coding memory hold up under noise?

The Vulnerable Moment: Personalization, Exploitation

Is Opus 5.5 nerfed? Thinking patterns changed on November 3