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?

Universe and the First Cause

Oseberg Tapestry Fragments

How Close Are We to Autonomous Chip Design

Microsoft Decision-1: 9B Qwen Model Launch Explained

What managing emergencies at Burning Man teaches me about incident management

Show HN: Drint – packaging dielines and 3D box mockups as an MCP server

New research tries to defuse the "China shock"

Handy page for dealing with your nearby emotionally bypassed human

Anthropic sued for allegedly using 274 Elvis Presley songs to train AI models

Brazil elections: Lula secures fourth term after dramatic comeback

Mantle – Agentic API Maintenance

JaJa: Job Agency Harness

The Designer Fallacy

Ask HN: Does your company require human review of AI-generated code?

Can They Write a Function?

FileBot Forums (phpBB) have been hacked

ARM1: Chip That Changed the World of Computing

If AI displaces human workers, they will lose more than just pay

Biff 2.0.4: LLM Skills

Show HN: God – real-time control room for LLM agent societies (EMNLP 2026 demo)

U.S. birth rate drops to record low, but older women are having more babies

iPhone Duo Teardown [video]

The subreddit each age is most over-represented in, women vs. men

IBM CEO says open weight models are now irresistibly good and cheap on-prem

Data centre debate heats up ahead of US midterms

Recycling ANSI art: Tracing the origins of Fire Escape's BBS logon screens

Show HN: Little Fun Games – daily trivia with uncommon-answer scoring

Grokking: A 777-Parameter Transformer Learned Real Math

iPhone Duo Teardown

Cve.now: A Free Feed of Security Vulnerabilities for Agents