django - 使用 prefetch_lated(model_SET).all() 获取相关模型外键(除了 ManyToMany 之外)

Question

通过 prefetch_lated，我可以检索不同仓库库存的列表，如下所示:

模型产品

[没什么特别的]

模型仓库

[没什么特别的]

型号 SstStock

class SstStock(models.Model):
    warehouse = models.ForeignKey(Warehouse, on_delete=models.CASCADE)
    product = models.ManyToManyField(Produit)
    qty = models.IntegerField()
    last_update = models.DateTimeField(default=timezone.now)

views.py

class ProductListView(LoginRequiredMixin, ListView):
    queryset = Product.objects.prefetch_related('sststock_set').all()
    context_object_name = "produits"
    paginate_by = 10
    template_name = 'products/produits.html'

    def get_context_data(self, *args, **kwargs):
        context = super(ProductListView, self).get_context_data(
            *args, **kwargs)
        context['title'] = 'Produits'
        return context

模板

{% for produit in produits %}
    {{ produit.sku}}<br>
    {% for sst in produit.sststock_set.all %}
        <span>{{ sst.warehouse.code }} - {{sst.qty}} - {{sst.qty}}</span>
    {% endfor %}
{% endfor %}

但是当我获得与仓库相关的信息时，例如。模板中的sst.warehouse.code，查询数量爆炸式增长。 (已经有 36 个查询，分页只有 10 个产品)

有没有办法在 View 中的prefetch_lated中添加warehouse？

Answer 1

您可以使用 Prefetch object [Django-doc] :

class ProductListView(LoginRequiredMixin, ListView):
    queryset = Product.objects.prefetch_related(
        Prefetch('sststock_set', SstStock.objects<strong>.select_related('warehouse')</strong>)
    ))
    # …

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Note: Django's DateTimeField [Django-doc] has a auto_now=… parameter [Django-doc] to work with timestamps. This will automatically assign the current datetime when updating the object, and mark it as non-editable (editable=False), such that it does not appear in ModelForms by default.