如何在Django中的一个查询中计算一个字段和相同但已过滤的字段？

Question

I'm really not a web developper so sorry for the title of my question that doesn't really make sense.

To make things easier, here are what my models look like (I stripped non necessary fields for the demonstration):

class User(models.Model):
    username = models.CharField(max_length=100)
class Vote(models.Model):
    user = models.ForeignKey(AskFmUser)
    date = models.DateTimeField('vote date')

And in a view, I need to list all users, with the number of votes they received, ordered by votes. I have no problem doing this, with this Query :

global_votecount = Vote.objects.all().values('user', 'user__username').annotate(votesTotal=Count('user__username')).order_by('-votesTotal')

And in my template, I display it on a table with two columns (username, and vote count).

But what I need to do, is display the total vote count they received all time, but also, in this same HTML table, the name of votes they received today .

I know I can get votes for today with this query:

now = timezone.now()
today_votecount = Vote.objects.filter(date__year=now.year, date__month=now.month, date__day=now.day).values('user', 'user__username').annotate(todayVotesCount=Count('user__username')) 

But the problem is that if no votes were made for a specific user during the day, he would not appear in the list. Also, the list, even if ordered with an order_by, would be ordered differently.

So... do you see any "clean" solution to be able to get the total vote count and the vote count for a timeperiod (by filtering in the "date" field), in a single query ? If not possible... could I manually go though these two ValuesQuerySet to add a field in the first one (corresponding to "today votes count", when a username is found in the second one ?

Thank you

Answer 1

I'm not sure how to do it in one query, but consider something like this:

global_votecount = Vote.objects.all().values('user', 'user__username').annotate(votesTotal=Count('user__username')).order_by('-votesTotal')

import datetime
today_min = datetime.datetime.combine(datetime.date.today(), datetime.time.min)
today_max = datetime.datetime.combine(datetime.date.today(), datetime.time.max)

votesToday = dict(Vote.objects.filter(date__range=(today_min, today_max)).values_list('user__username').annotate(votesToday=Count('user__username')))


for item in global_votecount:
    item['votesToday'] = votesToday[item['user__username']]

This uses two queries, and takes the results of the second and applies it to the results of the first query.