Comment by andatki

Hi there. Thanks for the feedback. I updated that section to hopefully convey the intent more. The type of ordering we care about for this topic is really B-Tree index traversal when inserting new entries and finding existing entries (single and multiple values i.e. an IN clause, updates, deletes etc). There's a compelling example I re-created from Cybertec showing the pages needed and accessed for equivalent user-facing results, comparing storing PKs as big integers vs. UUID v4s, and how many more pages were needed for v4 UUIDs. I found that to be helpful to support my real world experience as a consultant on various "medium sized" Postgres databases (e.g. single to 10s of millions of records) where clients were experiencing excessive latency for queries, and the UUID v4 PK/FKs selection made for reasons earlier was one of the main culprits. The indexes wouldn’t fit into memory resulting in a lot of sequential scans. I’d confirm this by showing an alternative schema design and set of queries where everything was the same except integer PKs/FKs were used. Smaller indexes (fit in memory), reliable index scans, less latency, faster execution time.