Thanks, Rajesh, that most definately helps. I figured that I'd have to resort to something like option #1 after many google searches.
On 10/17/07, RajeshD <[EMAIL PROTECTED]> wrote: > > > Hi Jason, > > > Using the models below I'd like to be able to create Querysets such as: > > > > a = Treatment.objects.filter(total_dose__range=(4000,10000)) > > b = a.filter(tumor__patient__gender = 'M') > > > > Both of the above work, but then I'd like to have an additional filter: > > c = b.filter(tumor__patient__get_followup_length__gt = 5) > > This is not possible because get_followup_length is not a field in the > DB table but a model class method and Django doesn't support that > (because it can't build a SQL statement out of this queryset > definition.) > > Here are some alternatives: > > Option #1. Add a followup_length field to your Patient model. Rename > the method get_followup_length to compute_followup_length and change > it so that it stores its computed value into the new followup_length > field. > > Then, call compute_followup_length() from delete() and save() methods > in Tumor. In other words, everytime Tumor is changed, its Patient's > followup_length gets computed. You can also achieve this via signals > if you don't want to override Tumor.delete() and Tumor.save(). See: > http://code.djangoproject.com/wiki/Signals > > Option #2. Filter the result set in memory using standard Python: > c = [x for x in b if x.tumor.patient.get_followup_length() > 5] > > Note that, if you expect c to have a lot of rows, this will load them > all in memory. And, obviously, c will be a list rather than a > queryset. > > Hope this helps. > > -Rajesh > > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/django-users?hl=en -~----------~----~----~----~------~----~------~--~---
