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?

Your Child's privacy is worth more than likes (2022)

Open-source, agent-friendly accounting platform

Energy – Work at the Speed of Thought

Stop Feeding the Machine: Time to Go Closed Source

Cashing in on SpaceX: 'Every chance I get, I'll sell a little more'

Lumetry, a RAW photo editor that never uploads your photos

Transparent AI Labeling

Gemini Robotics Released One Policy from Feet to Fingertips

Putin signs landmark crypto law allowing regulated retail trading in Russia

Because the machine must break (true empowerment in the age of AI tools)

Ask HN: Is there any Hacker News but for investing/trading/economics etc.?

State-Oriented Consistency: Why We Stopped Looking for One Right Answer

Doortrackr

Why police raided Starbucks Korea's headquarters

Onida – Leading Home Appliance Brand in India

The Wind at Your Back

Unconscious Inference

Ask GitHub SRE: How serious is the situation there?

Depot CI Compatibility with GitHub Actions

Google is talking about Gemini 4 while 3.5 Pro remains delayed

Agent Plugins Specification

The Printer

LettuceDetect v2 in Semantic Router: Gen. Hallucination Detection vLLM Endpoint

Reducing AppSec false positives with paraconsistent logic instead of thresholds

AI can now design functional viruses – not the computer kind, either

Continual Learning via Real-Time RL for Agents

Cynicism and Naïveté in the Summer of a Thousand Fires

The DISTINCT in Your COUNT

Large genome models used to design new viruses

xAI Ignores Laws and Profits: Rules for Thee, Not for Me