PostgreSQL Indexes: First principles
> <i>Sequential isn’t Always the Worst</i><p>Indeed! And sometimes it gets even more nuanced - when say the way the index(es) would be used would imply a lot of disk seeking (or page faults if not the whole of index(es) is/are in memory (you can "pre-warm" them into memory but if you have to do that you may have to go back to your schema and index design and re-assess it anyway)). Sometimes a bulldozer-like (mostly) (hopefully!) sequential disk read works better.<p>The latter becomes tricky with say SSDs - you then may need to inform Postgres of differing costs for (e.g.) disk seeks (or memory reads vs. disk reads) so it can better decide which way to go.