[storm] Mixing explicit and implicit joins

[Shaun McCance]

I'm trying to figure out how to force a single left join while
still getting implicit joins with other tables.  Here's a very
stripped down version of what I've got:

Branch
  ident
  mod_person_ident (-> Entity)
Entity
  ident
SetModule
  subj_ident (-> ReleaseSet)
  pred_ident (-> Branch)

Here's the wrong version:

store.find((Branch, Entity),
  Branch.mod_person_ident == Entity.ident,
  Branch.ident == SetModule.pred_ident,
  SetModule.subj_ident == "something")

The problem is that with doesn't return any Branch objects
where mod_person_ident==None.  This does what I want:

join = (LeftJoin(Branch, Entity,
          Branch.mod_person_ident == Entity.ident),
        SetModule))
store.using(join).find((Branch, Entity),
  Branch.ident == SetModule.pred_ident,
  SetModule.subj_ident == "something")

This does what I want.  The problem is that this all happens
in a utility function that returns a ResultSet.  That utility
function takes *args just like store.find, and it could be
called without a reference to SetModule, or with a reference
to some other table.

So I'd like to get the same implicit list of tables I get
with store.find, but force that single left join.  If there
were some function to scan *args and give me a list of the
tables I need, that would do the trick.

Any ideas?

--
Shaun