如何在 Django 查询集中重新创建 reddit 排序？

Question

作为一个学习项目，我认为在 Django 中创建一种 reddit 克隆会很有趣。 This is where I‘m at right now. My next step is to implement the reddit sorting. I found the algorithm here. If it helps, this is the sorting in sql.

我能够在模型中将其设置为属性，但不会保存到数据库中，这意味着您无法对其进行排序。因此，为了对其进行排序，我一直在尝试使用 annotate() 和 aggregate() 函数在查询字符串中重新创建排序算法。但是，我还没能走多远。

所以我的问题是：如何在 Django 中重新创建 reddit 排序算法？

这是我的 views.py（的一部分），它不起作用并且在第 33 行之后丢失了很多东西，尽管用于获取分数（赞成票 - 反对票）和排序的注释函数它，确实有效：

import pytz
from pytz import timezone
from datetime import datetime, timedelta
# from math import log

from django.shortcuts import render, get_object_or_404, redirect
from django.core.urlresolvers import reverse
from django.core.paginator import Paginator, EmptyPage, PageNotAnInteger
from django.http import HttpResponseRedirect
from django.contrib.auth.decorators import login_required
from django.contrib.contenttypes.models import ContentType
from django.db.models import F

from .models import Link, Comment
from .forms import LinkForm, CommentForm

# the reddit sorting algorithm
# epoch = datetime(1970, 1, 1, tzinfo=pytz.utc)
#
# def get_epoch_seconds(date):
#     """Returns the number of seconds from the epoch to date."""
#     td = date - epoch
#     return td.days * 86400 + td.seconds + (float(td.microseconds) * 1000000)
#
# def reddit_sort(score, date):
#     order = log(max(abs(score), 1), 10)
#     sign = 1 if score > 0 else -1 if score < 0 else 0
#     seconds = get_epoch_seconds(date) - 1134028003
#     return round(sign * order + seconds / 45000, 7)

def links(request):
    all_links = Link.objects.annotate(
        total_score = F('upvotes') - F('downvotes'),
    ).aggregate(
        Case(When(score__lt=0, then=Value(-1)),
            When(score__gt=0, then=Value(1)),
            default=0
        ) * Func('LOG', (Max(Abs(total_score), 1) + (EPOCH(F('date')) - 1134028003) / 4500)
    ).order_by('total_score')

    paginator = Paginator(all_links, 10) #show 10 links per page
    page = request.GET.get('page')

    if request.method == 'POST':
        if request.user.is_authenticated():
            form = LinkForm(data=request.POST,auto_id=True)
            if form.is_valid():
                form.full_clean()
                form.save()
                return HttpResponseRedirect('/')
        else:
            return HttpResponseRedirect('/accounts/login/?next=/')
    else:
        form = LinkForm(auto_id=True)
        try:
            links = paginator.page(page)
        except PageNotAnInteger:
            # in case of invalid page, serve homepage, should probably add error message
            links = paginator.page(1)
        except EmtyPage:
            # If page is out of range (e.g. 9999), deliver last page of results.
            links = paginator.page(paginator.num_pages)
    return render(request, 'posts/links.html', {'links': links, 'form': form})

Answer 1

您是否正在尝试实施 the "hot" sort（还有其他几种特定于 reddit 的类型）？

reddit 将链接（和评论）的排序值存储在排序缓存中；投票处理器然后计算新的排序值并存储它。这最终比尝试在查询中进行即时排序计算要容易得多，就像您正在做的那样。它通常也更有效，因为您每次投票只会进行一次计算，而您的方法将在每个 read.[=11 上重新计算每个 post 的排序值=]

如何在 Django 查询集中重新创建 reddit 排序？

How to recreate reddit sorting in django queryset?

python

django

algorithm

sorting

reddit