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

1•LawZiL•10mo 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•10mo 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•10mo 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•10mo 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•10mo ago

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

Fine-Tuning Large Language Models LLMs with a Production-Grade Pipeline (2023)

Leapstack-vn-data-breach-approximately-100-GB-of-health-insurance-claims

The Technocracy Movement of the 1930s

Period – 11M params car parking model

'A System Rigged': Untaxed Wealth of Richest 0.1% More Than Poorest Half

EPA Targets Microplastics and Drugs in Drinking Water

Jobs Being Created by AI

Can I say, "Thank You"?

A tool to help product write better specs

The Unreasonable Effectiveness of Cash Transfers

How to Mirror from Sourcehut to GitHub

Every dependency you add is a supply chain attack waiting to happen

Rancho Gordo trademarks 'bean club,' tells others to stop using it

Axios Maintainer Confirms Social Engineering Attack Behind NPM Compromise

The FusionAuth Brainf* SDK

Run a Local LLM, and discover why LLMs are unpredictable

The open web isn't dying. We're killing it

Tesla March car registrations soar in key European markets

How to Set Up Work and Personal Git Profiles

Slightly safer vibecoding by adopting old hacker habits

Help on Posts

Neoen to Build France's Largest Battery Amid Strained Power Grid

Artemis II commander enters tablet PIN on launch livestream

Pinterest and Shopmy for AI-powered fashion shopping

All the Worst People Seem to Want to Be 'High Agency'

Pay to PrAI: Insert Coin to Try Again Podcast

Making TinyLLM Go Brrrrr

Paul Graham, Founder Y Combinator [video]

Timeline of Microsoft's SmartNIC Tech (Azure Boost)

Mars Terraforming Research Roadmap