为了避免耗时且昂贵的精确数据库计数查询,我想覆盖count()
Django 管理类中的方法如下所示:
from django.contrib import admin
from django.db import connection
class CountProxy:
def __call__(self):
# how to access the queryset `query` here?
query = ...
try:
if not query.where:
cursor = connection.cursor()
cursor.execute("SELECT reltuples FROM pg_class WHERE relname = %s", [query.model._meta.db_table])
n = int(cursor.fetchone()[0])
if n >= 1000: return n # exact count for small tables
return object_list.count()
except:
# exception for lists
return len(object_list)
return estimated_count
class MyAdmin(admin.ModelAdmin):
def get_queryset(self, request):
qs = super(MyAdmin, self).get_queryset(request)
qs.count = CountProxy()
return qs
但我不知道如何访问我的原始查询集CountProxy
班级。任何想法?我知道我可以覆盖整个changelist
浏览get_changelist
。但这涉及到 Django 存储库中的大量重复代码。
我可能是错的,但你能通过吗qs
作为实例属性CountProxy
?
class CountProxy:
def __init__(self, query):
self.query = query
def __call__(self):
# you've already had the query here, do something with self.query
class MyAdmin(admin.ModelAdmin):
def get_queryset(self, request):
qs = super(MyAdmin, self).get_queryset(request)
qs.count = CountProxy(qs)
return qs
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