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?

Show HN: PartSense – Smart inventory and BOM management for hardware labs

Show HN: AI Meter – Local token usage with energy and water estimates

Names with the largest count in their first appearance on the national list

Can AI Run a Food Truck Business?

Kimi K3's Design Secret May Be in Its Thinking Traces

Classical Acceptance Is Not Hybrid Authentication: Measuring X.509 Verifier

Black Perl

Japanese Firm to Train Robot with AI to Reproduce Runners' Movements

Setting up a remote environment for agentic coding on a VPS

Cut Token Costs in Half

IT Atlas

Show HN: RMCP.dev – An MCP server that finds other MCP servers

Fountible: Agentic Figma

Reddit Calls Anthropic a 'Freeriding Pirate'

Starship's Thirteenth Test Flight

Hannah Fry Wins the Leelavati Prize in 2026 for Mathematics Outreach

US moves to regulate hidden car handles

Show HN: Maps of >100 theories for how society works inc. Graham / Thiel / Smith

IBM Acquiring HRL Laboratories

Midjourney Releasing v8.2

Pliny the Liberator claims universal jailbreak of models

Trump's Plan for Science: More Money for A.I., Less for Universities

22 Years of Rails

Show HN: Codebeat – turn any function into a song (no signup)

A Great Deal of Information About Hacker News

Show HN: Jolta – Automatic per-project JDK switching (like Volta, for Java)

Ukraine' Simple But Effective Protection Against Russian Starlink Jamming (2023)

Exercise Erased Half the Molecular Signature of Muscle Aging

Evaluation of a pentapropellant upper stage (1970) [pdf]

Show HN: Modelfac