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?

1,600 C reactor can melt raw Moon dust into finished solar cells, glass and wire

IBM Outlines Sub-1nm Nanostack Transistor Technology

What is the best way to get survey answers?

Tabularis: Open-source desktop SQL client your AI agent can use

Code review is dead. Long live code review

Windows 10 quietly gets one more year of support and updates

Measuring tech debt in tokens instead of engineering hours

Show HN: Use AI once to build the automation, then run it with $0 in AI

Show HN: VibeDrift – measuring AI coding drift across open source repos

The Boeing 747 Begins Its Final Descent

Cultures of Making and Relating

Ghostty/Agents.md

Technical feedback on a client-side microkernel enclave?

Daytona is going closed source

In Meta's Reality Lab: Your body's data was only valuable once

The principle of least power (2007)

YouTube Video ID Allowance

Everyone's Been Drawing Pterosaur Wings Wrong

Object-oriented OS with many features of popular niche Linux distributions

Show HN: Hikaru Labs – Bulk image and file processing, 100% in-browser

Calling everything AI-generated is lazy

A Herculaneum scroll has been read for the first time

Billionaire's Warning: I'm Selling. The Crash Is Here [video]

Claude Code Hints at Fable Return

The Trump White House Is over Anthropic CEO Dario Amodei

What if some of history's earliest kings were queens?

Route Through Dead Zones. 302x Faster Than Google

My New Life with the Palantir Chore Coat

Anthropic accuses Alibaba of largest distillation attack to date

Ask HN: Do you thank your agents when they did a good job?