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

1•LawZiL•9mo 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•9mo 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•9mo 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•9mo 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•9mo ago

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

Show HN: Free, serverless Redis clone backed by Durable Objects

UK Cryptography Developer claims IP to protect UK National Security was stolen

Show HN: Tmuzika – terminal music player written in C (ncurses and GStreamer)

We open sourced a rite of passage for the permanent underclass problem

Impressions from Mozilla 1.2B (2002)

When is AI coming to CAD design?

Separation of direct and globalscvene components using HF illumination

Learnings from Building an AI Root Cause Analysis Agent

An Open Source SDK and Runtime for Building Agents

Apple Blocks US Users from Downloading ByteDance's Chinese Apps

Unstract: Open-source platform to ship document extraction APIs in minutes

Meta's Renewed Commitment to Jemalloc

Ignoring the Wisdom of Crowds

If photons have no mass, how can they have momentum?

Uber is letting women avoid male drivers and riders in the US

Deterministic metrics for requirements quality (IEEE 830, no LLM)

Show HN: MessyData – Synthetic dirty data generator

Tanker War

Helix 02 Living Room Tidy [video]

Un hack me now mate

Show HN: The Mog Programming Language

Show HN: OpenClix, Agent friendly, open-source retention tooling

eInk wall remote for HomeAssistant – fed up with tablets and hacked Kindles

Show HN: DocTracker – track client documents and send reminders

Models have some pretty funny attractor states

Show HN: We built an MCP server so LLMs can self-correct against business rules

Seldom: An Anonymity Network with Selective Deanonymization

Use /loop to run Claude Code on a Schedule

AI agents are coming for government. How one big city is letting them in

The Government Told Courts It Could Easily Refund Tariffs. Now It Says It Can't