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

1•LawZiL•10mo 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•10mo 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•10mo 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•10mo 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•10mo ago

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

Vibe Coding a (basic) Wispr Clone in 20 minutes

You Can't Escape the AI Tax

Rejected by iloveimg so created ihateimg

Ollama Now Runs Faster on Macs Thanks to Apple's MLX Framework

Google lets you ditch that embarrassing old Gmail username

Show HN: Lazy-tool: reducing prompt bloat in MCP-based agent workflows

Fast sandboxed code execution with pre-warmed gVisor pools

From "Show Me" to "Do It": How OdooClaw Takes Action in Your Odoo

Show HW: How This Graybeard Built the Fastest and Freest Postgres BM25 Search

Show HN: LeetChess – Solve Chess Puzzles on New Tab Pages

Cohere Transcribe: Speech Recognition

Sigil CMS – headless CMS with native multi-tenancy, 22 plugins, GraphQL and CLI

Show HN: PhAIL – Real-robot benchmark for AI models. The gap to humans is 20x

Why some American accents have endured – while others have faded away

AI agent that writes and hot-reloads its own Python modules at runtime

Show HN: Wageslave – I quit my soul sucking job to make a game about it

Forth VM and compiler written in C++ and Scryer Prolog

The Last Fingerprint: How Markdown Training Shapes LLM Prose

Interaction Nets

Build with Veo 3.1 Lite, our most cost-effective video generation model

Analyzing Geekbench 6 Under Intel's Binary Optimization Tool (Bot)

Ask HN: What are you building with AI coding agents / tooling?

The Overvaluation Trap (2015)

I made a 3D Browser to review my HN upvotes [video]

Building a Powerful SIEM with ClickHouse and Clickdetect – Wazuh – SQL Detection

How Congress Plans to Take on the Housing Crisis

DuckLineage Extension for DuckDB

Are New York's Environmental Concerns Worsening a Housing Shortage?

Create Issues from Slack with Copilot

What Maxxing Reveals About Life Online