Hi Yeb
Thanks for the pointers.
Of course disk access is not obsolete: As I said, I suppose changes are streamed to disk.
When I mentioned "no disk access" I meant the indices of RDBMS which designed to handle disk access - which seems to me different in in-memory dabases.
The paper referred by you is coming from SAP's chief scientist and it confirms actually my claim, that there's no need for a primary index since the primary attribute (i.e. all attributes) is already kept sorted in-memory.
It also mentions an insert-only technique: "This approach has been adopted before in POSTGRES [21] in 1987 and was called "time-travel".
I would be interested what "time-travel" is and if this is still used by Postgres.
Finally the paper is mostly about column stores - nothing about persistence. In mentions Disaster recovery" in the last section about future work, though.
-S.