It has good points, but has 2 major problems, IMHO, that we observed when I was part of a team building a RDBMS:

* It again ignore the best solution for nulls: Algebraic types. Once you have this much get solved for free

* The argument against bags:

The best idea of the paper is that a RDBMS in fact internally do different data structure and temporal representations that are not of concern to the user. Correct.

THEN it jumps to the conclusion that bags should not be presented to the user, despite the fact acknowledge it need to display them.

This is wrong, and the major reason that is always overlooked is that assume that 2 identical values are wrong to exist.

I can have "Jhon, Jhon", be 2 separate persons, not know at this time more to disambiguating, adding a Id do nothing to help me, and yet, this data is correct as is.

The language MUST allow me to deal with this. It will absurd to claim an array language, procedural, functional, imperative, declarative, etc can and a relational can't.

It say the lang is intentionally limited for purity, that true, is ideal in some cases, but that purity is what the engine/compiler should track, but not distort MY DATA for this.

And the part where the perf of having bags dismissed is easy to debunk: implement a dbms and profile.

P.D: Is true that set unlocks lots of benefits, and in some cases are ideal. But very fast once you hit the real world you see that need both, similar how btrees alone is not enough, and then there is hash-based indexes and many others.

it sucks, but reality is unfriendly to pure pure languages

P.D.2: And to clear misunderstanding, I agree with the points in the same way Rust say the borrow checker is ON by default, but I argue we CANT make a strict rule, in special because data is not ideological pure

Time to Move On: Querying Without Nulls and Bags