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?

Semantica, the Open Source Palantir for AI Agents

Show HN: FerrumPix Photo/RAW-Editor, Viewer, Gallery, Immich & Nextcloud Client

Show HN: Overcoming silicon-level aging through fault tolerance (PoC)

Show HN: A new way to read books, magnifying in and out

PINE64 halts their open-source hardware manufacturing until the AI bubble bursts

China Saved the Global Oil Market

Everyone's Using This A.I. Dictation App That I Want to Murder with a Hammer

Show HN: Bests and Worsts Reviews from Amazon

Show HN: A free accessibility scanner that says what it can't check

Two Memory Management Optimizations Going into Linux 7.3

Corsair Cove

Japan to require AI firms to disclose training data

Two hours from idea to a live URL

Orion: The open-source agentic BI platform

Flight attendants and pilots have highest risk of dying from radiation cancers

Collaborative Human Agent Protocol (CHAP)

Open-fx: forked fx to run on subs

Claude Opus 4.6: 900/900 zero-byte executions under a frozen protocol

Composing CRDTs Convergent by Construction

Plain Text Accounting Is Pretty Cool

Node.js AI use policy and guidelines

Ask HN: We have company runway but not founder time. When do you go full-time?

When William Schneiderman and California Communists Defeated the Smith Act

Reclaim the Terminal

I hijacked my Hacker News habit to learn Spanish

Cicada.os Graphene.os for Your Laptop

Sing-song: a speakable encoding for long numbers and keys

OpenInfer Cloud: Free Access for Creative Developers

Show HN: A React component optimized for 1987

Programming Lewis Carroll's Memoria Technica (2024)