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?

Why are we still writing separate extensions for VS Code, JetBrains, and Zed?

White Rabbit – sub-nanosecond synchronization for large distributed systems

Show HN: Ifmhy – An Internationalization Version of Fmhy

Embedded acoustic AI with <16ms latency running on 8MB RAM

BambuStudio has been violating PrusaSlicer AGPL license since their fork

Concerning Emacs (and Jazz)

Show HN: Chord Commander – A webapp to organize guitar chords

SpaceX IPO: Nice Try Though [video]

A New Supercarrier Emerges Tracking China's Fourth Aircraft Carrier

Legends of the Ancient Web (2017)

Building an AWS Lambda-Like Runtime with Firecracker MicroVMs

Does anyone in your organisation own "correctness" in your AI products?

ChatGPT as the AOL of AI

Ask HN: How do small teams securely share env files?

Pausing New Challenges – Codecrafters

I reproduced a Claude Code RCE. The bug pattern is everywhere

Show HN: GobanFTP – the board game Go played through FTP listings

The three futures nobody is building for

You're Being Judged

Nobody Understands Kafka Costs

Show HN: Klimkit: my Codex setup for multiple machines

Twelve Ways to Be Wrong About AI-Assisted Coding

AI Ops SOP Pack: SOPs for reviewing AI-assisted engineering work

Show HN: Source-check politician stock-trade claims against public filings

Don't Read the Comments

An interactive linear algebra primer aimed at LLM readers

The most RAM efficient modern Linux. Noctalia v5 and LabWC and Artix [video]

AI Reconstructed Dead Pilots' Voices from Public NTSB Records

Show HN: Larksson-lang: everything is a map or an atom

Experience: We found a baby on the subway – now he's our 26-year-old son