[SQLObject] Re: Relation Awareness

[Randall S. <ra...@tn...>]

While it is on my mind, what would a good syntax be for this.

I initially thought.

A.select(C)
A.select(C.q.name == 'dog')

Currently, that does a Cross Join.  I've never seen a need to use a 
Cross Join, but I sure don't want to change this functionality.

Another idea.  Use a keyword.

# These only work if a multiple join is already defined.
A.select(multiple_join=(C.q.name == 'dog', ))
A.select(multiple_join=(B.q.status == 'A', C.q.name == 'dog'))
Z.select(multiple_join=(B.q.status == 'A', ))

#For a concrete useful example, let's talk about drinking water because
#I work in drinking water regulation.

Entitys:  WaterSystem -> Facility -> SamplePoint -> Sample -> Results

# Each relationship is a MultipleJoin.

# All SamplePoints for a WaterSystem
sample_points = SamplePoint.select(multiple_join=WaterSystem)

#Say I want a list of cyanide sample results for active SamplePoints
#for WaterSystem 0200001 with a level > .02 mg/l after 2005-01-01.

results = Results.select(multiple_join=(AND(
     WaterSystem.q.st_id == '0200001', SamplePoint.status == 'A',
     Sample.date_coll > datetime.datetime(2005, 1, 1),
     Results.anl_code = '1024', Results.result > 0.2))

This may be some errors in there, but maybe you get the point.  The 
point is that I've already told SQLObject how objects are related when I 
defined the classes, so I shouldn't need to do it again.  It should be 
able to figure out how these things are related.

Randall