更快的Django Admin Paginator:无法使此Django代码段正常工作 [英] Faster Django Admin Paginator: Cannot get this Django snippet to work
问题描述
我在Django管理员列表中找到了用于提高大型数据库表查询性能的代码段:
I found this snippet for improving the performance of large database table queries in Django admin lists:
https://djangosnippets.org/snippets/2593/
在使用时存在一些问题它与Django 1.10一起使用,在我之前的问题中已经讨论过:
There are some issues about it when using it with Django 1.10, which are already discussed in my previous question here:
如何使用PostgreSQL计数估算来加快Django管理页面的速度?
尤其是, _count
需要重命名为 count
和 query_set
到 queryset
。这是该代码段相关部分的简短版本:
Particularly, _count
needs to renamed to count
and query_set
to queryset
. Here's a short version of the relevant part of the snippet:
from django.core.paginator import Paginator
from django.core.cache import cache
class FasterAdminPaginator(Paginator):
def _get_count(self):
if self.count is None:
try:
key = "adm:{0}:count".format( hash(self.object_list.query.__str__()) )
self.count = cache.get(key, -1);
if self.count == -1 :
if not self.object_list.query.where:
# estimates COUNT: https://djangosnippets.org/snippets/2593/
cursor = connection.cursor()
cursor.execute("SELECT reltuples FROM pg_class WHERE relname = %s",
[self.object_list.query.model._meta.db_table])
self.count = int(cursor.fetchone()[0])
else :
self.count = self.object_list.count()
cache.set(key, self.count, 3600)
except:
# AttributeError if object_list has no count() method.
self.count = len(self.object_list)
return self.count
count = property(_get_count)
问题是,我仍然无法正常工作。当前错误日志摘录:
Problem is, I still cannot get it to work. Current error log excerpt:
maximum recursion depth exceeded while calling a Python object
...
result_count = paginator.count
...
if self.count is None:
不知道如何使代码片段正常工作。
No idea how to get the snippet working.
推荐答案
我认为我们可以将分页器拖入django 1.10世界中(希望不是
I think we can drag that paginator into the django 1.10 world (hopefullly not kicking and screaming) like this:
from django.core.paginator import Paginator
from django.core.cache import cache
from django.utils.functional import cached_property
from django.db import connection
class FasterAdminPaginator(Paginator):
@cached_property
def count(self):
try:
if not self.object_list.query.where:
# estimates COUNT: https://djangosnippets.org/snippets/2593/
cursor = connection.cursor()
cursor.execute("SELECT reltuples FROM pg_class WHERE relname = %s",
[self.object_list.query.model._meta.db_table])
print 'Using the reltuples'
ret = int(cursor.fetchone()[0])
else :
return self.object_list.count()
except :
import traceback
traceback.print_exc()
# AttributeError if object_list has no count() method.
return len(self.object_list)
对 cached_property 不再需要原始摘要中使用的大量缓存代码。为了完整起见,这是 django.core的relevent部分。 .paginator.Paginator 看起来是
Thakns to cached_property the extensive caching code used in the original snippets are no longer needed. For completeness, this is what the relevent section of django.core.paginator.Paginator looks like
@cached_property
def count(self):
"""
Returns the total number of objects, across all pages.
"""
try:
return self.object_list.count()
except (AttributeError, TypeError):
# AttributeError if object_list has no count() method.
# TypeError if object_list.count() requires arguments
# (i.e. is of type list).
return len(self.object_list)
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