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?

LinguaHover – Hover Any Word, Translate Instantly – Chrome Extension

Show HN: Mochi Analytics

Ask HN: Do you like your AI more than your coworker?

In the Weights

Bounding the Blast Radius: A Survey of Prompt-Injection Defenses for LLM Agents

What Happens When AI Agents Can Pay Their Own Bills

Higher blood glucose levels linked to faster brain aging

Supply Chain Attack Campaign PolinRider

Poll: Is there an AI bubble?

Generative AI without guardrail can harm learning:Evidence from high school math

Tribe in Colorado brings utility scale solar project online

Claude Code deletes conversations after 30 days

Adding Homemade TLS to a Homemade Web Server

Euclid scientists discover most distant known quasars

Ask HN: What is your go-to prompt to prove AI can be wrong?

Ask HN: Do you guys struggle with finding a right person for your FDE role?

Experts offer advice on performing endurance events in excessive heat

Read Rust Like a Chinese Character

A Self-Improving Code World Model Agent

Show HN: Kiwi – Run agentic dev loops in the cloud, keep keys on your laptop

Plex debuts 5-year membership pass for $250

Australia prosecuting Amazon for unilaterally modifying Prime terms [video]

Show HN: I built notion database based no code form builder

The Hitchhiker's Guide to Agentic AI

Show HN: TV Time to Serializd Importer

your competitor is 10x better than you

What else happened in 1776 [video]

Venice AI becomes a unicorn with its privacy-first AI platform takes off

China fires ballistic missile into Pacific nuclear-free zone

Roll your own file-based router in under 50 lines of code