Faster Django Admin Paginator：无法使此 Django 代码片段正常工作

Question

我在 Django 管理列表中找到了用于提高大型数据库 table 查询性能的代码段：

https://djangosnippets.org/snippets/2593/

将它与 Django 1.10 一起使用时会出现一些问题，这些问题已在我之前的问题中讨论过：

特别是，_count 需要重命名为 count，query_set 需要重命名为 queryset。这是该片段相关部分的简短版本：

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，我仍然无法让它工作。当前错误日志摘录：

maximum recursion depth exceeded while calling a Python object
...
result_count = paginator.count 
...
if self.count is None:

不知道如何让代码段正常工作。

Answer 1

我认为我们可以像这样将分页器拖到 django 1.10 世界中（希望不要踢和尖叫）：

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)

他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看起来像

@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)

Faster Django Admin Paginator：无法使此 Django 代码片段正常工作

Faster Django Admin Paginator: Cannot get this Django snippet to work

django

performance

admin

paginator

code-snippets