The problem is that Set is superfluous, oddly named, and thereby makes
the whole DAL confusing to learners. I experienced this confusion
myself when learning web2py, and now I find it's a problem when
teaching web2py to others.
A Query is not, as some web2py docs claim, just a WHERE clause. It
superficially resembles a WHERE clause, but it also implicitly encodes
the joining of tables. A Set only represents the same virtual set of
rows that the Query it wraps, so why keep Set and its confusing name?
Off the top of my head, here's the simplest fix:
1. The Query class should gain the Set methods, e.g.:
(db.mytable.id == 3).select()
2. And for queries/updates of a single table, give Table these methods
as well, e.g.:
db.mytable.select()
Instead of:
db().select(db.mytable.ALL)
The special case db() is particularly confusing: all other Sets
represent a Query, and a Query only represents multiple tables in the
form of joins (which effectively means combining tables into one); the
db() Set is the only case of a Set that represents multiple, unjoined
tables. It's weird.
I'm sure there are use cases I haven't accounted for, but unless there
are under-the-hood concerns I'm not aware of, I think it fairly
evident that Set can be gotten rid of without much fuss. Am I totally
wrong?
