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?

Final run for the current LHC accelerator (but more to come)

Have politics come for the National Academies of Science?

Hacking Salesforce Sites with an LLM Agent

Why the US economy keeps defying the odds

Anthropic Is Taking AI Welfare Seriously. I'm Not Sure It Knows What It's Measu

I accidentally hit SOTA on agentic memory by using AI companions

Local Models in Mid-2026

Google's Pinpoint is the free research tool you should know about

Untrusted data in Linux – How Rust is going to save us

One-click, production-like ATProto network for local development and E2E testing

Levyer: The Platform. Designed for Freedom

HumanizeHub: A confidential marketplace for humanizing AI content

While Oracle Will Rake in Big Bucks on AI, Profits Are Hard to Predict

Upscaling Space Quest 3 [video]

Network service termination for certain Sony Electronics products

Sygnet – Hash any document with SHA3-512 and declare your AI usage level

Zuckerberg says Meta made 'mistakes' in AI workforce shift

Superpowers for Claude, Codex etc.

Nockchain vs. Pearl: The Great Compute War

A Rant about IPOs

Trial of 12mph bike lane speed limit grinds gears of Dutch cyclists

Cursed Knowledge

An architectural blueprint to excise MS-DOS device debt (CON, NUL) from Windows

New Brunswick woman sues OpenAI, alleging ChatGPT led to daughter's death

Don't trust large context windows

China Is Propping Up the World Economy by Importing Less Oil

Introduction to (Multimodal) LLM-as-a-Judge

Mining And refining: uranium and plutonium (2024)

How an astrophysicist uses Codex to help simulate black holes

AI: Surgeon's Assistant or Commodity on a Meter?