Question

我遇到queryset.intersection(...).filter(...)的问题。我发现filter()调用根本不执行任何操作，但返回的结果与queryset.intersection()相同。

我现在提供一个说明性示例。 minex/models.py个文件：

from uuid import uuid4

from django.db import models


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


class Release(models.Model):
    version = models.CharField(max_length=255)
    uuid = models.CharField(max_length=100, default="")
    channels = models.ManyToManyField(to=Channel, related_name='releases')

    def save(self, *args, **kwargs):
        if not self.uuid:
            self.uuid = str(uuid4())

        super(Release, self).save(*args, **kwargs)


class Serial(models.Model):
    name = models.CharField(max_length=255)
    releases = models.ManyToManyField(to=Release, related_name='serials', blank=True)

问题的说明：dbtest.py

import os
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'minexample.settings')
from minexample.wsgi import application
from minex.models import Serial, Release, Channel

channel = Channel.objects.create(name="stable")

r1 = Release.objects.create(version="1.0")
r1.channels.add(channel)
r06 = Release.objects.create(version="0.6.2")
r06.channels.add(channel)

serial = Serial.objects.create(name="Some Serial")
serial.releases.add(r06)

releases = serial.releases.all().intersection(channel.releases.all())

assert r1 not in releases  # works as expected

assert not releases.filter(uuid=r1.uuid).exists()  # assertion failed... why?

注意：如果我们改为releases = serial.releases，则最后一个断言不会失败。问题似乎是我在打电话给intersection()。我还进入了Django的代码，WHERE语句根本不包含uuid=r1.uuid ...这是一个错误还是我做错了什么？

Answer 1

在应用filter()之后，Django现在给出错误消息，通知不支持intersection()：

https://code.djangoproject.com/ticket/31227

Django queryset.filter（）在intersection（）结果上不起作用

1 个答案: