Hi Simon,
Thanks for the clarification of the operation of the .union() method - the
operative phrase in the docs appears to be "combine the results of two or
more QuerySets" - perfect!
My project is currently using 1.8 LTS - I can defer this until I roll
forward to 1.11 LTS (hopefully sometime soon).
Thanks again,
R.
On Sat, Jun 3, 2017 at 6:31 PM, Simon Charette <charett...@gmail.com> wrote:
> Hello Richard,
>
> Since Django 1.11 you should be able to use the QuerySet.union() method[0]
> for that.
>
> queryset = self.many_field1.order_by('some', 'fields')
> combined = queryset.union(self.many_field2.order_by('some', 'fields'))
>
> Best,
> Simon
>
> [0] https://docs.djangoproject.com/en/1.11/ref/models/querysets/#union
>
> Le samedi 3 juin 2017 20:20:11 UTC-4, Richard Brockie a écrit :
>>
>> Hi,
>>
>> I am combining querysets of the same model in the following manner:
>>
>> class ExampleModel(models.Model):
>> many_field1 = models.ManyToManyField('Model', related_name='name1')
>> many_field2 = models.ManyToManyField('Model', related_name='name2')
>>
>> def combined_many_fields(self):
>> qs1 = self.many_field1.all().order_by('some', 'fields')
>> qs2 = self.many_field2.all().order_by('some', 'fields')
>>
>> return qs1 | qs2
>>
>> The result of the above code is that the order_by() methods are applied
>> after the querysets are combined. This means that the two querysets can
>> intermingle. I want them to be sorted before combination, not after, and
>> retain being a queryset.
>>
>> There are ways to force the evaluation of the individual querysets first
>> and return a combination in the preferred order.
>>
>> def combined_many_fields(self):
>>
>> from itertools import chain
>>
>> return chain(qs1, qs2)
>>
>> However, this is no longer a queryset, and therefore cannot be operated
>> on with subsequent queryset methods. Is there a way to apply the ordering
>> first and retain the queryset nature of the combination?
>>
>> Am I trying to do something that is outside the scope of a queryset?
>>
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--
R.
Richard Brockie
Real-time bicycle race results - www.ontheday.net
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