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?

A proper Docker image for WebCalendar: SQLite-backed and self-contained

Jiki – Learn to Code the Fun Way

The Hard-Line Activists Ramping Up for the War with AI

The Gen X Career Meltdown (2025)

In Praise of Exhaustive Destructuring

AST vs. Bytecode (2023) [pdf]

When They Steal Our Future

Shark: The First Light Aircraft That Cancels Turbulence [video]

School Is Not Enough

Ghostel.el: Terminal emulator powered by libghostty

Show HN: DejaView – Terminal dashboard for all your Claude Code sessions

Growing list of countries move to ban social media for children

Vyrai – a travel challenge where your age is your flight budget

Show HN: Godot running Gemma 4 inference in GDScript and Vulkan compute shaders

Show HN: Markdown Tools Online – 16 free browser-based Markdown converters

Reaction: A daemon that scans program outputs for repeated patterns, and takes a

Puffin-Inspired Robot That Swims and Flies [video]

We are now factory engineers, not product engineers

Finetuning a Reasoning LLM with Supervised or Reinforcement Learning?

Political Neutrality Benchmark of popular AI models

Short Reflection on being Offline for 24 hours

xs: Concatenative array language inspired by kdb+/q in OCaml

Edge Password Bulk Manager

NetBSD as a Desktop: A Nostalgic '90s Experience

Teleflow: A local-first teleprompter and selfie recorder for creators

Show HN: LifePath – See what Einstein was doing at your exact age

Forget "Fat" Models. The Future Is Narrow

Show HN: InLie – See manipulation tactics in political videos, live

I Built a WordPress Plugin Nobody Asked For. Here's Why –. and How

Stop Getting 'Good' at ChatGPT (2024)