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?

New Bitcoin Fee Pressure Signal

Global Biolab Map

Staged Publishing for NPM Packages

Moe inference optimizations: 15% lower expert load by request reordering

Show HN: A fast, free AI rewriter

Model Thinking – Percolation Models (2020) [video]

Shareable text box

Boundaries – A Talk by Gary Bernhardt

DOS Zone

Everything Is Computer: On Palantir's Manifesto and the Recompiling of the State

Step by step guide: How to install Microsoft Office in any Linux distribution

China Wants A.I. To Flourish, but Not at the Expense of Jobs

Node.js TypeScript: The future of –experimental-transform-types

Can one run AI on source code with the prompt "Find below-avg swear rate files"?

TheLounge v4.5.0 released – a modern, self-hosted web IRC client

Franklin Pierce by David W. Blight

Alan's ASI Checklist

Why Many Americans Choose Not to Have Children

Font licensing is about to change

The AI economy is rewriting the American Dream

Productivity Growth in the U.S. Medical Care Sector [pdf]

Starbucks cold plastic cups don't make it to recycling, probe finds

Google accused of pushing 'free for life' G Suite users onto paid plans

If you can't get a job today, it's your fault

Open Weight Music Generation Models Trained on Licensed Data

Jewish American Security Act requires online platforms to moderate purge content

Open AI solves a 1946 Erdős problem

The Developer's Guide to AI

Medieval China's Lost Ocean Empire

Even Claude agrees: hole in its sandbox was real and dangerous