Django多对多字段：Queryset值

Question

I have the following in django 1.8 :

class Author(models.Model):
    first_name = models.CharField(max_length=255)
    last_name = models.CharField(max_length=255)
    @property
    def full_name(self):
        return u"{0} {1}".format(self.first_name, self.last_name)

class Article(models.Model):
    title = models.CharField(max_length=10, unique=True)
    authors = models.ManyToManyField(Author)

I would like to get a queryset that has the following format:

results = [{"title":"title1","authors":['first_name last_name', 'first_name last_name']

So all the many_to_many objects are grouped into a list.

The query i'm used to perform for these cases is :

results = Article.objects.all().prefetch_related('authors').values('title','authors')

I can solve the issue by looping into each object and constructing a new dictionary, but it becomes a bottleneck after +100 items.

    results = []
    for element in Article.objects.all().prefetch_related('authors'):
        results.append(dict(title=element.title, 
authors=[b.full_name for b in element.authors.all()]))

Is there a django way to solve this issue ?

Answer 1

Something I would try is the following:

results = []
authors = Author.objects.only('full_name')
qs = Article.objects.only('title').prefetch_related('authors', queryset=authors)
for element in qs:
    results.append(
        dict(
            title=element.title, 
            authors=[b.full_name for b in element.authors.all()]
        )
    )

OR

results = []
qs = Article.objects.select_related('authors').only('title', 'author__full_name')
for element in qs:
    results.append(
        dict(
            title=element.title, 
            authors=[b.full_name for b in element.authors.all()]
        )
    )

This basically amounts to reducing the amount of data fetched from the server by querying only the required columns and then trying select_related instead of prefetch_related (whether this helps or not depends heavily on the your actual data).