在Wa中使用图像标签时，许多重复的查询 [英] Many duplicate queries when using image tag in Wagtail

问题描述

我正在将Wagtail v1.13.1用于我的网站项目.我正在尝试优化数据库查询...

I'm using Wagtail v1.13.1 for my website project. I'm trying to optimize db queries...

models.py

class ProductPage(Page):
    ...
    main_image = models.ForeignKey(
        'wagtailimages.Image', on_delete=models.SET_NULL, related_name='+', blank=True, null=True
    )

class ProductIndexPage(Page):
    ...
    def get_context(self, request, *args, **kwargs):
        context = super(ProductsIndexPage, self).get_context(request)
        all_products = ProductPage.objects\
            .prefetch_related('main_image__renditions')\
            .live()\
            .public()\
            .descendant_of(self)\
            .order_by('-first_published_at')
        paginator = Paginator(all_products, 10)
        page = request.GET.get('page')
        try:
            products = paginator.page(page)
        except PageNotAnInteger:
            products = paginator.page(1)
        except EmptyPage:
            products = paginator.page(paginator.num_pages)
        context['products'] = products
        return context

product_index_page.html

我正在for循环中输出产品卡.每个产品卡都有以下标签:

I'm outputting product card in a for loop. Each product card has this tag:

{% image product.main_image fill-600x300 %}

但是仍然为每个图像分别调用db.

But still getting a separate call to db for each image.

以这种方式连接模型:

产品页面 --fk-> wagtailimages.Image <-fk-- wagtailimages.Rendition

ProductPage --fk--> wagtailimages.Image <--fk-- wagtailimages.Rendition

问题是:预取演绎并消除重复的数据库查询的正确方法是什么?

The question is: What is the proper way to prefetch renditions and eliminate duplicate db queries?

推荐答案

尝试一下.

prefetch_related('main_image__rendition_set')

这是假设图像模板标签可以正确使用预取的值.

This is assuming that the image templatetag can use the prefetched values correctly.

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