> One question: as a novice here, I think I understand the right hand
> side of your JOIN "... k(value)" is shorthand for:
>
> ... AS table_name(column_name)
>
> except that I don't see any clues in the docs that
> jsonb_object_keys() is a "table function".> Can you kindly clarify?
The clue is in the column "return type" which states: "setof text" for jsonb_object_keys()
A function returning "setof" is the same as a "table function"