Thread

Re: Should we update the random_page_cost default value?

Greg Sabino Mullane <htamfids@gmail.com> — 2025-10-07T19:15:02Z

Fascinating thread. As the author of the previous thread Bruce mentioned
advocating a lower default rpc, I'm obviously highly invested in this.

On Tue, Oct 7, 2025 at 11:38 AM Robert Treat <rob@xzilla.net> wrote:

> One of the interesting things about Tomas' work, if you look at the
> problem from the other end, is that this exposes a thought-line that I
> suspect is almost completely untested "in the field", specifically the
> idea of *raising* random_page_cost as a means to improve performance.
>

I've been doing this sort of thing for clients a long time, and I always
test both directions when I come across a query that should be faster. For
real-world queries, 99% of them have no change or improve with a lowered
rpc, and 99% get worse via a raised rpc. So color me unconvinced. Obviously
finding some way to emulate these real-world queries would be ideal, but
alas, real client data and schemas tends to be well protected. One of the
take-away lessons from this thread for me is that the TPC-* benchmarks are
far removed from real world queries. (Maybe if we ask an LLM to use an ORM
to implement TPC-H? Ha ha ha!)

Cheers,
Greg

--
Crunchy Data - https://www.crunchydata.com
Enterprise Postgres Software Products & Tech Support