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?

Update for October 30th, 2026 Data Security Incident

Lessons from Building Copilot Cowork

Few Repercussions for Continued Gas Leaks After Couple's Death

GrapheneOS accuses YC of funding surveillance and enabling HN harassment

Andrew Weldon post mortem on his Quake 4 levels

If your code chatbot was genuinely honest

GEO600 – A Vacuum Leak in the North Arm (2017)

OneUptime 14.0: open-source observability platform adds data observability

show HN: Computer-Generated Asset Pipelines: Shading Language in Toy Story (1995)

AI Product Team – 64 specialized AI agent roles with executable CLI workflows

METR: Independent Assessment of AI R&D Acceleration at Anthropic in October 2026

Humans slowly change, and that is our chance

Piuma: New open source status bar for Hyprland

Stay ahead in AI race; Build on next AI Idea

VCF West Presentation: Is That Unix? – Sean Haas [video]

Harness 2: executing agent code as it streams

Devvm.dev: One VM for every project

Bye Deno, Hello Cloudflare

Apple's grey list: iPhone won't autocorrect 'male chauvinist pig'

When dreams feel real: the MÖBIUS model

Figma for hardware: AI can generate CAD, but what should we build?

The agentic web is here

Show HN: Thesis, checks every SEC filing against why you own a stock

Counting words-hacking human-cheat code

Ask HN: What have the past 12 months taught you?

Just how far can the FOR UPDATE SKIP LOCKED Postgres queue go?

Anthropic IPO valuation talks drop to $1.3T

OpenAI will keep investing in AI data centers despite election results

Doom 3 BFG source code review

Show HN: Wrapped – Your neighborhood's 311 story