Re: '{"x": 42, "y": null}'::jsonb != '{"x": 42}'::jsonb ... Really?

declare
  j1          constant jsonb   not null := '{"x": 42, "y": null}';
  j2          constant jsonb   not null := '{"x": 42           }';

(j1->>'y' is null)

(j2->>'y' is null)

  predicate_2 constant boolean not null := j1 = j2;

Another test (I won't bore you with its code) confirms that the order in which the incoming document lists key-value pairs has no consequence for its meaning.

  j1_in  constant jsonb not null := '{"a": 17, "b": null}';
  j2_in  constant jsonb not null := '{"a": 17           }';

This is the result:

{"a": 17, "b": null}
{"a": 17, "b": null}

I have a little demo where I shred a set of "books" incoming JSON documents (where a book has a genre and many authors) into the classic Codd-and-Date four tables: books, authors, genres, and book_author_intersections. Then I scrunch each book back to a single JSON doc. I want to prove that I get back what I started with.