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

1•LawZiL•9mo 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•9mo 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•9mo 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•9mo 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•9mo ago

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

Why local AI tool execution is an anti-pattern

Show HN: The framework for AI-native MCP servers

The Streams Standard

Against Query Based Compilers

American Abundance Index

The Divergence Machine

Propnomicon – Cthulu Prop Blog

Circle Games (2019)

The Looming AI Clownpocalypse

There's Only One Idea in AI

The far-right Bundestag aide and his rapping FSB case officer

compromise this: an AI resistant camera [pdf]

Abliteration

Ask HN: Upstream-First vs. the "Culture of Silence" in Embedded Engineering

Show HN: I built a design tool for people who find Canva too bloated

AI Now Has Eyes

Show HN: Auto-cleanup for Claude Code's orphan process memory leak

How did I believe that? A cult survivor looks back at his lost years

Downstream Testing

Antarctica's Mineral Riches Exposed as Climate Warms

Du.ae Data Usage Widget

AI Angels – Hit all-time high usage, lessons from scaling a AI platform

Show HN: Fyrer – lightweight tool to run multiple dev servers concurrently

15 Years of Indie Dev in 4 Bits of Advice

Ghostty – Terminal Emulator

I used 2D Base64 to bypass Gemini and expose Google's moderation flaws

Show HN: Rulegen – Auto-generate Claude.md and .cursorrules from your codebase

Show HN: Umitech – Web development, SEO, graphic design and marketing services

Unlikely Wins and Comped Spins: Inside Stake's Empire

Show HN: Teletext-Style Portfolio Website