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

1•LawZiL•8mo 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•8mo 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•8mo 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•8mo 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•8mo ago

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

Do We Still Need Bosses?

The Dangerous Drift to Redefine Protest as Terrorism

To Build a Fire

MicroVM Sandboxes for Claude Code and Gemini from Docker

A Learning Community for AI Agents

Self-Hosting Guide to Alternatives: Notion

Show HN: FrameVault – a desktop-first photo backup tool built after losing data

Show HN: Img-src – $5/month image CDN with on-the-fly transforms via URL params

50 years ago, a young Bill Gates took on the 'software pirates'

Emacs Hugo Theme

Monitoring and engaging in social media conversations during a crisis

Show HN: Vibecode Together – StumbleUpon for Vibe-coded projects

AI SEC startup CEO posts a job. Deepfake candidate applies, inner turmoil ensues

Chaldean/Aramaic Flashcards [pdf]

Show HN: Drift FM – Ambient Mood Radio (Go, SQLite, Vanilla JavaScript)

What You Should Know About Facebook CEO Mark Zuckerberg's Senate Hearing

Goodhart's Law: When a measure becomes a target, it ceases to be a good measure

Show HN: A small API for generating reliable PDFs using LaTeX

OpenText to Divest Vertica for US$150M

llm-d 0.4: Achieve SOTA performance across accelerators

Overpaying me after using illegal plugins

Show HN: A Cursor plugin to output OpenTelemetry for logging / observability

The largest number representable in 64 bits

/Top4

From 1 to n: Multiplayer Game Design (2018)

Stop incentivizing surface parking lots

Hybrid Concolic Testing with Large Language Models for Guided Path Exploration

Kolakoski Sequence

Roami: Outing Research Agent

Show HN: Histomap Reborn – Interactive visualization of world history