[英]Multiple annotate with sum and display data in admin - Django
我是Django和Python的新手。 目前我正在嘗試使用Django Admin。
我有三個Django應用程序模型,分別是GoodsItem
, SoldGoodsItem
和FinishedGoodsItem
。 models.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)
這是admin.py:
from django.contrib import admin
from django.db.models import Sum
from .models import GoodsItem, FinishedGoodsItem, SoldGoodsItem
@admin.register(SoldGoodsItem)
@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=Sum('finished_name__weight'),
sold_good=Sum('sold_name__weight'),
stock_available=Sum('finished_name__weight') - Sum('sold_name__weight'),
)
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):
return obj.stock_available
在stock_available
,每個GoodsItem
,我想顯示FinishedGoodsItem
所有條目和SoldGoodsItem
所有條目之間的SoldGoodsItem
。 現在,我得到的所有三個帶注釋的字段的值都是不正確的,這些字段是finished_good
, sold_good
和stock_available
。 我無法找到原因。 在Django Debug Toolbar中建議執行重復的查詢。
這是已知問題,當我們嘗試組合多個聚合時發生,如文檔中所述 。
作為此特定問題的解決方法,我們可以使用子查詢表達式。 這是我在get_queryset
方法中使用子查詢表達式更新的GoodsItemAdmin
。
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
希望有人覺得這很有用。
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