doc: rewrite random_page_cost description

Bruce Momjian <bruce@momjian.us>

Commit: d4e4cecace91bd91f77da1cf081df2dba1b76a41
Author: Bruce Momjian <bruce@momjian.us>
Date: 2025-10-30T23:11:53Z
Releases: 16.11
doc:  rewrite random_page_cost description

This removes some of the specifics of how the default was set, and adds
a mention of latency as a reason the value is lower than the storage
hardware might suggest.  It still mentions caching.

Discussion: https://postgr.es/m/CAKAnmmK_nSPYr53LobUwQD59a-8U9GEC3XGJ43oaTYJq5nAOkw@mail.gmail.com

Backpatch-through: 13

Files

PathChange+/−
doc/src/sgml/config.sgml modified +18 −18

Documentation touched