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?

How accurately did science fiction stories predict AI?

Dynamic force sensing by bone delays aging and extends lifespan in mice

Codetations: Rich, Granular, and Maintainable Annotations for Evolving Code

Stop Dirty Data Centres

From Linux to Wikipedia: How Volunteers Build the Internet

Servo Browser Engine Continues Broadening Web Compatibility, New Features

Personality traits are less stable than people think

OpenSSH flaw lets attackers log into password-disabled Linux accounts

Lilithbrown

Lab-grown meat was supposed to save the world. What happened?

18 Years of GOG – Anniversary Showcase

Bomb threats disrupt at least 25 flights across Europe, raising hybrid war fears

US FAA says it will phase out floppy disks from air traffic control by 2028

Apple Watch Live Rewind and Siri Recap: Features and Limitations

Running MicroPython on the Allwinner T527's XuanTie E906 RISC-V Core

Silicon Valley's Bad Night

AI and the Future of the Product Role

Are We Cooked? CMU Faculty on AI, Careers and Learning [video]

Meta Warns Midterm Backlash Threatens AI Data Centers

Letterboxd in Negotiations to Be Acquired by New York Times Company

Move fast and don't break (safety critical) things

Claude Code, but for SEO

Queen's University Belfast students find Neptune's elusive Trojan asteroids

Native macOS storage monitor with an interactive disk explorer

DApp's Numbers, with the Working Shown

Nvidia CEO called in by lawmakers over ties to alleged Chinese spy

What does LoRA specialized Muon optimizer even mean?

Vaucanson's Digesting Duck

Pwn.college

Show HN: NextGen WAF – Native Prolog Server and Rule System