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?

Swarm – open-source control center for Claude Code / Gemini / Codex agents

Intel Arc G3 Extreme Handheld Gaming Performance

Show HN: Zova – Objects, vectors and records in one SQLite file

Quake Turns 30 Today

The EF's New Structure

Trump's Prescription Drug Shakedown: How He Made Other Countries Pay Up

A skill pack that stops coding agents from agreeing with bad startup ideas

Show HN: Find and fix issues in your AI Agents (MIT, open source)

I sleep less when I exercise more

Running GLM-5.2 on a 64GB Mac, barely

Task Failed Successfully: Saturating NIC and Disk Bandwidth

FDA Allows New Sunscreen, but Consumers Are Still Being Burned by Cronyism

Pew Research: AI adoption is rising. Trust isn't

Anthropic – Elevated error rate across multiple models

European Parliament committee backs digital euro

Sunsetting Porto to focus on Tempo accounts

Show HN: TikZ Editor – WYSIWYG editor for figures in LaTeX

The AI Code Agent Hype: Real Progress vs. Expectations

Badakhshan Falls Under Mafia: Systematic Gold Mine Plunder, Taliban Corruption

Meta Glasses

Ask HN: How do you keep up with tech news

Vulgar Materialism

Second taskbar to my Windows PC

Show HN: Bun-sqlgen – Type-safe raw SQL for Bun, no ORM

Elevated error rate across multiple models

The eerie interface of man and machine (Life Magazine, October 1967)

The AI-powered World Cup runs on thousands of data workers

OctoPunk – a full-featured, AI-integrated GitHub client

Useful app changed how I use Windows 11's taskbar

Ushering in the Next Frontier of Quantum Innovation