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

1•LawZiL•9mo 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•9mo 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•9mo 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•9mo 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•9mo ago

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

German political spies mistook a random Berlin woman and got her fired

I'm Not Consulting an LLM

Game Theory #9: the US-Iran War [video]

Dotfiles for Consistent AI-Assisted Development – Dylan Bochman

When the chain becomes the product: Seven years inside a token-funded venture

Making Firefox's right-click not suck, more, with userChrome.css

Ask HN: Why there are no actual studies that show AI is more productive?

Show HN: Run any VLM on real-time video

What Automattic's AI Enablement Training Means for WordPress

Unredact

Ask HN: Meta ad / business account and pages gone

Show HN: Flora – Compile-time Dependency Injection for Go without reflection

Fantasque Player

Salt Typhoon hacked 80 countries – AT&T can't confirm hackers are out

Attackers prompted Gemini over 100k times while trying to clone it, Google s

Superpowers for Claude Code: Complete Guide 2026

Invoker Commands API

Show HN: Codebrief – Make sense of AI-generated code changes

Show HN: MindPlexa – Open-source AI-powered infinite canvas: Next.js, React Flow

SWE-CI: Evaluating Agent Capabilities in Maintaining Codebases via CI

SCRY 17-source research engine for Claude Code(no API keys, pure stdlib)

Show HN: Cursor skill for Claude Code's /loop scheduler

Show HN: Go LLM inference with a Vulkan GPU back end that beats Ollama's CUDA

I built a tool that tailor your resume and cover letter for every job in seconds

LLMs take the fun out of coding

Show HN: MOCC – Turn your MRR or follower milestones into beautiful mockups

New Research Reassesses the Value of Agents.md Files for AI Coding

Ask HN: Has finding more competitors ever made you more confident?

The Synthetic Data Playbook: Generating Trillions of the Finest Tokens

72 commits in a day, a third of them reverting the rest