> > Please do elaborate on this. AFAIK FKs in filter() work just fine, so
> > if there's something broken we should know about it right away.
>
> I found ticket 2076, but that only concerns order_by().
>
> I haven't got access to my code at the moment.
Ok, I got hold of my code.
Of course (I had a feeling that this was going to happen), the only places I
can find where I couldn't get filtering to work are where I'm doing
something that is probably too complex to do with SQL (although I'm no SQL
expert).
Here's the function I ended up with after trying to get it going with
filter() :
def exception_age(request, year_filter):
"""Lists cadets that might not be the right age for the course they
applied for."""
this_june = date(int(year_filter), 6, 1)
this_sept = date(int(year_filter), 9, 1)
apps = list(Application.objects.filter(year=year_filter))
# filter out any that are definitely the right age
apps = [a for a in apps if (a.cadet.age_on(this_june) <
float(a.camp.min_age)) or (a.cadet.ages_out() < this_sept)]
I don't have the filter() versions that I tried along the way, but it was
based on comparing the application.cadet.date_of_birth field.
This one involves comparing the values in two tables :
def exception_eligibility(request, year_filter):
"""Lists cadets not in the right level for the course they applied
for."""
apps = list(Application.objects.filter(year=year_filter))
# filter out any that are in the right level
apps = [a for a in apps if a.training_level < a.camp.min_training_level]
# Sort the list by squadron number
apps.sort(key=sqn_of_app);
return render_to_response('camps/exception_eligibility.html',
{'object_list' : apps,})
and this one requires doing a calculation on the difference between two
fields (cadet.date_of_birth and cadet.enrollment_date) :
def exception_enrollment(request, year_filter):
"""Lists cadets enrolled too young who've applied this year."""
apps = list(Application.objects.filter(year=year_filter))
# filter out any that joined old enough
cdts = [a.cadet for a in apps if a.cadet.age_at_enrollment() < 12]
# Sort the list by squadron number
cdts.sort(key=sqn_of_cdt);
return render_to_response('camps/exception_enrollment.html',
{'object_list' : cdts,})
I do have examples of where order_by doesn't work. Here's one :
def wing(app):
return app.cadet.sqn.wing.name
def camp_csv(request, year_filter, object_id):
[...]
app_list = list(camp.application_set.filter(year=year_filter))
# Sort by wing
app_list.sort(key=wing)
# app_list =
camp.application_set.filter(year=year_filter).order_by('camps_application__c
adet.sqn.wing.name')
[...]
You can see where I've commented-out what I wanted to do. The commented-out
version gives :
Exception Type: OperationalError
Exception Value: (1054, "Unknown column
'camps_application__cadet.sqn.wing.name' in 'order clause'")
This is following a series of foreign keys (application belongs to cadet,
belongs to sqn, belongs to wing).
Chris
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