多注释与总和和显示数据在管理Djang

Question

我对Django和Python都是新手。目前我正在尝试Django管理员做。在

我有三种Django应用程序模型，分别是GoodsItem、SoldGoodsItem和{}。这个模型.py是：

from django.db import models


class GoodsItem(models.Model):
    name = models.CharField(max_length=255)
    size = models.DecimalField(max_digits=4, decimal_places=2)
    INCHES = 'IN'
    NUMBER = 'NUM'
    GOODS_ITEM_SIZE_UNITS = (
        (INCHES, 'Inches'),
        (NUMBER, '#'),
    )
    size_unit = models.CharField(
        max_length=4,
        choices=GOODS_ITEM_SIZE_UNITS,
        default=INCHES,
    )

    def __str__(self):
        if(self.size_unit == self.NUMBER):
            return "%s #%s" % (self.name, (self.size).normalize())
        else:
            return "%s %s\"" % (self.name, (self.size).normalize())


class FinishedGoodsItem(models.Model):
    date = models.DateField()
    goods_item = models.ForeignKey(GoodsItem, on_delete=models.CASCADE, related_name="finished_name")
    weight = models.DecimalField(max_digits=6, decimal_places=3)

    def __str__(self):
        return str(self.goods_item)


class SoldGoodsItem(models.Model):
    goods_item = models.ForeignKey(GoodsItem, on_delete=models.CASCADE, related_name="sold_name")
    date = models.DateField()
    weight = models.DecimalField(max_digits=6, decimal_places=3)

    def __str__(self):
        return str(self.goods_item)

这是管理员py公司名称：

^{pr2}$

在stock_available中，对于每个GoodsItem，我想显示FinishedGoodsItem的所有条目和{}的所有条目之间的差异。现在，我得到的三个带注释字段的值都不正确，它们是finished_good、sold_good和{}。我找不到原因。在Django调试工具栏中，建议执行重复查询。在

Answer 1

这是一个已知的问题，当我们试图组合多个聚合时就会发生，如docs中所述。在

为了解决这个特殊问题，我们可以使用子查询表达式。这是我的最新消息管理员py在GoodsItemAdmin的get_queryset方法中使用子查询表达式。在

from django.contrib import admin
from django.db.models import Subquery, Sum, OuterRef

from .models import GoodsItem, FinishedGoodsItem, SoldGoodsItem

@admin.register(SoldGoodsItem)
class SoldGoodsItemAdmin(admin.ModelAdmin):
    fields = ('date', 'goods_item', 'weight')
    list_display = ('date', 'goods_item', 'weight')

@admin.register(FinishedGoodsItem)
class FinishedGoodsItemAdmin(admin.ModelAdmin):
    fields = ('date', 'goods_item', 'weight')
    list_display = ('date', 'goods_item', 'weight')

@admin.register(GoodsItem)
class GoodsItemAdmin(admin.ModelAdmin):
    list_display = ('__str__', 'finished_good', 'sold_good', 'stock_available')

    def get_queryset(self, request):
        qs = super(GoodsItemAdmin, self).get_queryset(request)
        qs = qs.annotate(
            finished_good = Subquery(FinishedGoodsItem.objects.filter(goods_item=OuterRef('pk'))\
                .values('goods_item_id').annotate(sum=Sum('weight')).values('sum')[:1]),
            sold_good = Subquery(SoldGoodsItem.objects.filter(goods_item=OuterRef('pk'))\
                .values('goods_item_id').annotate(sum=Sum('weight')).values('sum')[:1])
        )
        return qs

    def finished_good(self, obj):
        return obj.finished_good

    def sold_good(self, obj):
        return obj.sold_good

    def stock_available(self, obj):
        finished_good = 0 if self.finished_good(obj) is None else self.finished_good(obj)
        sold_good = 0 if self.sold_good(obj) is None else self.sold_good(obj)
        return '-' if (finished_good == 0 and sold_good == 0) else finished_good - sold_good

希望有人发现这个有用。在