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?

Ask HN: Why are Spec-kit specs like that

Philippines now China's 2nd biggest market for solar panels

Neuroscientists discover cognitive benefits of reading physical comic books

When Tailwinds Vanish

Returning to Zig

Why Reddit blocked unauthenticated JSON in 2026

You probably don't need private PKI for internal infrastructure

Mid-tier US knives vs. cheap imports

T1A Brings Its Full Data Stack to Dais 2026: 5 Products AndSubscription Giveaway

Show HN: Fastembed-rs – Rust library for generating vector embeddings, reranking

Browser game about movie guessing

Nike Launches Sneaker Line with Russian Designer Who Backed Crimea Annexation

Graphtatui: In terminal graph explorer made with ratatui

Yield Curves and Volatility Surfaces Are Built in Modern Finance

CPMpy: Constraint Programming and Modeling library in Python, based on NumPy

Why Digital Twins Need Low-Latency Data Processing

Githipedia – The Wiki for GitHub

Show HN: I wrote a C++ ray tracer from scratch without AI

Ask HN: How do you handle browser tab overload?

Coversubstack-Zagreus=Whiterabbit.flexe

LibAgar – Cross-platform GUI written in C

What are you looking for when reviewing LLM generated code?

Ask HN: Developers, are you being forced into prompt-only engineering?

Fear about young adults' maturity is just a way of trying to control them (2023)

Show HN: ELDC – Natural language identification, faster than FastText and CLD2

Anthropic flies staff to D.C. to clean up White House fight

Trailblazing investigative reporter Roger Cook dies

Searching for Guy Debord (2003)

Ask HN: Did you try Claude's "Fable 5" model before it was pulled?

How to Think about Parallel Programming: Not (2010)