将 django RawQuerySet 转换为 Queryset [英] Convert django RawQuerySet to Queryset

问题描述

我有 2 个 Django 模型，ModelA 带有一个 ArrayField，用于存储一个大的主键值列表(可能是 50k+ 列表)

I have 2 Django models, ModelA with an ArrayField that is used to store a large list of primary key values (possibly 50k+ list)

class ModelA(models.Model):
    pk_values = ArrayField(models.IntegerField())

class CustomManager(manager.Manager):

    def get_for_index(self, index_id):
        qs = self.get_queryset()
        obj = ModelA.objects.get(pk=index_id)
        return qs.filter(id__in=obj.pk_values)

class ModelB(models.Model):
    # [...] some fields

    objects = CustomManager()

这有效:

qs = ModelB.objects.get_for_index(index_id=1)

然而，如果pk_values"是一个大列表，这将是非常慢的.

However, this would be super slow where "pk_values" is a large list.

所以我尝试做原始 SQL 查询:

So I tried doing raw SQL queries:

class CustomManager(manager.Manager):
    def get_for_index(self, index_id):
        qs = self.get_queryset()
        sql = "SELECT * FROM myapp_model_b JOIN myapp_model_a ON myapp_model_b.id = ANY(myapp_model_a.pk_values) WHERE myapp_model_a.id = '%s'" % index_id
        return qs.raw(sql)

但这会返回一个 django.db.models.query.RawQuerySet 实例.

But this returns a django.db.models.query.RawQuerySet instance.

但是有了这个，我之后就不能做queryset.values()之类的事情了.

But with this, I cant do things like queryset.values() afterwards.

如何将其转换为普通的 Django 查询集?

How can I convert this to a normal Django queryset?

有没有更好的方法来做到这一点?

Is there a better way of doing this?

文档:

• ArrayField https://docs.djangoproject.com/en/2.0/ref/contrib/postgres/fields/#arrayfield
• 自定义管理器 https://docs.djangoproject.com/en/2.0/topics/db/managers/#custom-managers-and-model-inheritance
• 原始查询 https://docs.djangoproject.com/en/2.0/topics/db/sql/#performing-raw-sql-queries

推荐答案

您可以使用 RawSQL 表达式:

You can use a RawSQL expression:

ModelB.objects.filter(id__in=RawSQL(
    'SELECT unnest(a.pk_values) FROM app_modela a WHERE a.id = %s',
    [index_id]
))

或者，您可以使用 重现您在问题中的确切查询extra():

ModelB.objects.extra(
    tables=['foo_modela'],
    where=[
        '"app_modelb"."id" = ANY("app_modela"."pk_values")',
        '"app_modela"."id" = %s',
    ],
    params=[index_id],
)

这篇关于将 django RawQuerySet 转换为 Queryset的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！