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djangopython-3.xdjango-1.7

How to combine select_related() and value()? (2016)


I am asking this question again (it was asked back in 2009),

We know there is a values() method of QuerySet, when there is a foreignkey (author, for example), it result like:

[{ 'author_id':3, ... }, ...]

I want a result like:

[{ 'author':{'name':'dave',...}, ... }, ...]

Has something changed in the newer versions of Django?

I want to convert the query set into a combination of lists and dictionnaries, is it possible?

I will then take this object and place it into a bigger object to serialize it. It is the reason why I don't want to serialize it right away.


Solution

  • You can access related fields via values() without the necessity to use select_related() (only these will be fetched without subsequent lookup):

    MyModel.objects.values('author__id', 'author__name')
    

    This will return the following structure:

    [{'author__id': 1, 'author__name': 'Dave'}, {...}]
    

    If you need it in a nested structure you would have to transform it afterwards.

    Note that for M2M relations, this returns one list entry per M2M relation, so probably not a desired effect. But for OneToOne/ForeignKey relations it works just fine.

    EDIT: for M2M relations annotate() in combination with values() works fine.