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?

How Can America Be So Miserable When It's So Rich?

Old-Games.com

Algorithms, Neo-Brokers, and Political Power Reshaping Who Wins on Wall Street

An LLM's not going to tell you no (2024)

Families are fed up with social media

Ask HN: Will AI ever be cheap?

The surprising science behind red-light therapy – and how it works

You shouldn't use ultrathink in Claude Code

Building a Blog with Elixir and Phoenix

Unit: A self-replicating Forth mesh agent running in a browser tab

Scientists discover popular diabetic drug's unexpected effect on the brain

CDC plans hiring push to fill gaps from last year's widespread layoffs

Spotify and Labels Seek $322M Default Judgment Against Anna's Archive

Germany's Merz floats EU-China trade deal as European capitals soften on Beijing

Online legal database CanLII and AI startup Caseway settle copyright dispute

Text Reconstruction via Subtle Vibrations from Videos

The surprising photographers behind Google screensavers

Ask HN: How do people control Claude Code on the go nowadays on the go?

Remote SQLite access your remote SQLite databases locally

Army extends maximum recruitment age to 42, allowing older recruits to join

Deploying MuJoCo on Azure ML: Surprising Pain Points

Why LLMs Lie in Different Ways?

System Stability Protocol [REF-333]: Axiomatic Logic and Entropy Minimization

SuperMicro sued by shareholders over China-related criminal case

GLP-1 Anti-Obesity Rx and Alcohol and Substance Use Disorders

Android Sets New Record for Mobile Web Performance

Clojure: The Documentary, official trailer [video]

Leadership – Bold Visionary, Technocratic Expert, or Trimmer

Helix – Self-healing SDK for AI agent payments

Harvey Raises at $11B Valuation