Django语句作用域视图查询

Question

我有三个模型，Result，Environment和Test。 Environment和Test是Result中的FK。我试图在给定的Result中为每个Environment找到最新 Test-本质上是为Environment生成一个页面，该页面显示每个Result的最新Test。

在尝试优化PostreSQL查询的过程中，我想到了以下内容：

WITH CR
AS
(SELECT "cases_result"."test_id",
max("cases_result"."created_at") "created_at"
FROM "cases_result"
WHERE "cases_result"."environment_id" = 1001
GROUP BY "cases_result"."test_id"
)

SELECT CR.* ,
"cases_test"."id",
"cases_test"."created_at",
"cases_test"."updated_at",
"cases_test"."name",
"cases_test"."usage",
"cases_test"."result_id",
"cases_test"."health",
"cases_test"."variance",
"cases_test"."duration",
"cases_test"."required",
"cases_test"."ticket",
"cases_test"."removed_at"

FROM CR
JOIN "cases_test"
ON CR."test_id" = "cases_test"."id"
ORDER BY CR."test_id" ASC, CR."created_at" DESC

我现在尝试查看是否可以在我的models.Manager中实现此功能。我目前有：

        tests = Test.objects.order_by('name')
        if environment.domain != 'example.com':
            tests = tests.exclude(name__startswith='sample')

        results = (
            self.filter(test__in=tests, environment=environment)
            .select_related('test')
            .prefetch_related('test__teams')
            .order_by('test_id', '-created_at')
            .distinct('test_id')
        )

        for test in tests:
            for result in results:
                if result.test == test:
                    yield result
                    break

我可以使用Django ORM创建此查询，还是需要使用原始SQL并获取关联的结果对象？

Answer 1

您可以为此使用django-cte。

他们的示例代码是：

from django_cte import CTEManager, With

class Order(Model):
    objects = CTEManager()
    id = AutoField(primary_key=True)
    region = ForeignKey("Region", on_delete=CASCADE)
    amount = IntegerField(default=0)


cte = With(
    Order.objects
    .values("region_id")
    .annotate(total=Sum("amount"))
)

orders = (
    cte.join(Order, region=cte.col.region_id)
    .with_cte(cte)
    .annotate(region_total=cte.col.total)
    .order_by("amount")
)