Django查询集select_related().values()重命名键

Question

使用 Python 3.4 和 Django 2.0.2

models.py

class Userinfo(models.Model):

    useruid = models.BigAutoField(db_column='UserUID', primary_key=True)

    useremail = models.CharField(
            db_column='UserEmail', unique=True, max_length=100)
    userpassword = models.CharField(db_column='UserPassword', max_length=128)

    passwordsalt = models.CharField(db_column='PasswordSalt', max_length=128)
    userstatus = models.IntegerField(db_column='UserStatus', default=0)
    username = models.CharField(
        db_column='UserName', max_length=100, default=0)
    class Meta:
        managed = False
        db_table = 'userinfo'

class Postinfo(models.model):
    postuid = models.BigAutoField(db_column='PostUID', primary_key=True)
    content = content = models.TextField(db_column='Content')
    useruid = models.ForeignKey(
    Userinfo, db_column='UserUID', on_delete=models.CASCADE)

    class Meta:
         managed = False
         db_table = 'postinfo'

查询集

postquery = models.Postinfo.objects.all().select_related("useruid").order_by(
                '-postuid')

postquery是什么？

<QuerySet [{'content': 'test','postuid': 1, 'useruid_id': 1},OtherPosts...>

并且

userinfoquery = postquery.values("useruid_id__username","useruid_id__userstatus","useruid_id")

userinfoquery is

 <QuerySet [{'useruid_id__username': 'firstuser','useruid_id__userstatus': 0, 'useruid_id': 1},OtherUsers...>

我希望将 useruid_id__username 翻译为 username

将 useruid_id__userstatus 翻译为 userstatus

将 useruid_id 翻译为 useruid

我尝试过这样做

userinfoquery = postquery.values(
                useruid="useruid_id", username="useruid_id__username", userstatus="useruid_id__userstatus")

这段代码会引发异常。

QuerySet.annotate() received non-expression(s): useruid_id, useruid_id__uesrname, useruid_id__userstatus.

如何删除用户uid_id__？

- Adam

Answer 1

从Django 1.11开始，你可以使用表达式来操作values()，请查看发行说明。因此，你需要向查询中添加F表达式：

from django.db.models import F
userinfoquery = postquery.values(
                useruid=F("useruid_id"), username=F("useruid_id__username"), userstatus=F("useruid_id__userstatus"))

- neverwalkaloner

---

引发此异常：“注释'useruid'与模型上的字段冲突。” postquery.values()中没有useruid。 - Adam

Answer 2

你可以使用注释功能

from django.db.models import F

Postinfo.objects.annotate(renamed_value=F('useruid_id__username')).values('renamed_value')

- Robert