I wonder what is the best flow when I need to retrieve foreign key model objects.

Question

I wonder what is the best flow when I need to retrieve foreign key model objects.

prefetch_related。就像:

queryset = queryset.prefetch_related( book_set )
context={objects:queryset}

或在模板中直接使用model_set:

{% for attach in objects.book_set.all %}

业绩更好些什么?

Answer 1

最佳办法取决于您的具体使用案例以及贵国数据库的内容和规模。然而,在<代码>views.py<>code>中,一般使用prefetch_related,可以通过减少数据库查询,提供更好的业绩。

下面是澄清这两种做法的一个例子:

Using prefetch_related() in views.py:

# views.py

queryset = Book.objects.all().prefetch_related( author )
context = { books : queryset}

<!-- template.html -->

{% for book in books %}
    {{ book.title }} by {{ book.author.name }}
{% endfor %}

在这一方法中,prefetch_related ( author ) fetches all relevant author in a individual query, reduction the number of databasefalls.

Using model_set in the template:

<!-- template.html -->

{% for book in books %}
    {{ book.title }} by
    {% for author in book.author_set.all %}
        {{ author.name }}
    {% endfor %}
{% endfor %}

在第二种做法上,每张<代码>book.author_set.all打上数据库,以检索相关作者的物体。这可能导致多个数据库查询和不同类型的问题,特别是如果你有大量书本的话。

I wonder what is the best flow when I need to retrieve foreign key model objects.

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