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?

Developer APIs for parsing and tailoring CVS

Bubble Sort Game

Show HN: Tracking iCal feed latency across O365/Google/Apple

Sorry, my software is better with agents

Plotnine

Hey, N00B, We Didn't Hire You to Complete Tasks

Show HN: The Deconstructed VS Code

A coin toss isn't random. Maybe our choices aren't either

PageToMD – A CLI tool to turn web pages into clean Markdown for AI agents

Vibe Coding at Scale? Engineering Strikes Back

Switching AI Tools Mid-Sprint Cost Us a Day (and What We Learned) – Week 6 R

Gistpreview.github.io: Gist HTML Preview

LUKS suspend failed to wipe volume encryption key from memory since Linux 6.9

Why local AI – and why it matters

Braess's Paradox

Bobby Prince's Doom (1993) Soundtrack Inducted into Library of Congress

Phoebus Cartel

Build your own vulnerability harness

Finding the Link Uber Missed: How to Connect AI Code Spend to Business Value

Show HN: NetSentinel – a local network security scanner and connectivity monitor

BookMarkr – Local first visually organized bookmark Chrome extension

Unreal deprecrates Blueprints, their visual programming language in UE6.1

Lakehouse//RT: Real-Time Performance on a Unified Lakehouse

How to Drive an LLM

What 'Getting Your Hands Dirty' Means at LLM-Era

The new HTTP QUERY method explained

Gemini provides phone number of scammer posing as Delta Airlines

Ask HN: What do you use for scientific presentations?

Show HN: UAVs FYI – Drone database with supply chain data, API and CLI

GLM-5.2: Chop off 84% of the volume from a 1.5TB model, still retain 82% power