Django查询与order_by，distinct和限制在Postgresql [英] Django query with order_by, distinct and limit on Postgresql

问题描述

我有以下内容：

class Product(models.Model):
    name = models.CharField(max_length=255)

class Action(models.Model):
    product = models.ForeignKey(Product)
    created_at = models.DateTimeField(auto_now_add=True)

我想检索由created_at DESC订购的10个最新动作，包含不同的产品。

I would like to retrieve the 10 most recent actions ordered by created_at DESC with distinct products.

以下是接近结果但仍然错过了排序：

The following is close to the result but still misses the ordering:

Action.objects.all().order_by('product_id').distinct('product_id')[:10]

推荐答案

您的解决方案似乎正在尝试做太多事情。它还将导致2个单独的SQL查询。这可以正常工作，只需一个查询：

Your solution seems like it's trying to do too much. It will also result in 2 separate SQL queries. This would work fine and with only a single query:

action_ids = Action.objects.order_by('product_id', '-created_at')\
    .distinct('product_id').values_list('id', flat=True)

result = Action.objects.filter(id__in=action_ids)\
    .order_by('-created_at')[:10]

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