FROM r JOIN s on r.Id = s.Id ORDER BY r.Id SELECT *
But the thing is, such changes will break pretty much all existing code, so the author added |> to distinguish, but why not use | instead? Don't make people typing one more character please.
FROM r JOIN s on r.Id = s.Id ORDER BY r.Id SELECT *
would indeed be pretty much that (linebreaks optional): FROM r JOIN s on r.Id = s.Id
|> ORDER BY r.Id
|> SELECT *
The question about “typing one more character” is answered in the paper's section 4.1.5 “Why use ‘|>’ for the pipe character?” (page 6): “The most natural and obvious choice would be to use ‘|’. Unfortunately…” — they don't want to break existing queries that use | for bitwise OR.(I wonder if one day, if the majority of users are using pipe syntax and don't mind updating their old queries or adding a special directive to enable single pipe…)